For an overview, here's a plot of where on Earth the occultation is visible. The star will first blink out for observers in Africa. Then the path goes acros the ocean, and will be visible in South America a few minutes later.

The mission decided to put most of its eggs in the Senegal basket (20 telescopes), and send a smaller crew to Colombia (3 telescopes). I was part of this Colombia-bound group.

The line here shows the rough position and width of the shadow path. The `true' position of the centerline was unknown, due to uncertainty in the position of both Ultimate Thule and the star.

Here's the single-plot summary of what we're trying to do. This is plot of observations done in 2011 by members of the International Occultation Transit Association (IOTA). This was a stellar occultation by the asteroid Antiope. Each line represents the light hitting one telescope on the ground. A single observer gives you a single line, which may or may not even hit the asteroid. But enough observers (56 here, mostly amateurs!), and you can map out the shape of the asteroid, and even look directly for binaries, just like shown here. So cool! MU69 is much smaller, much further away, much fainter... but conceptually, the same idea as this.

The decision of where to observe from is based on weather and logistics. Both Senegal and Colombia are near the equator, so their summer weather can be pretty rainy. Venezuela and Mali were off-limits to us, for safety reasons.

The shadow is moving at some 20 km/sec from east to west. The solid lines mark the 'best guess' position near the center. The event can be seen from any site on the line -- exactly where (east-west position) doesn't matter, as long as you are on the line.

Check out that apropos sign greeting us upon arrival at the airport! Colombia is not as famous as Chile in terms of astronomy, but it does have elevation! At 8700', Bogota itself is the third-highest capital in South America, after Quito and La Paz. As for the bicycle, tune in for the last day of our trip.

And here we all are at our home base at our hotel in Bogota! The six of us from the US are here, as well as Joel Castro from UNAM-Ensenada (Mexico). We started going over the maps and talking about possible areas to observe from.

NB: I observed in 2008 from the telescopes run from UNAM-Ensenada. The mountain ridge where the telescopes are is also home to dozens of California Condors -- turns out the San Diego Zoo has a major breeding program there.

Our leader Rodrigo Leiva (SwRI-Boulder), along with Aart Olsen (amateur from Champaign-Urbana). Check out those mountains behind us! We're enjoying the cool, cloudy weather of Bogota.

Joel Castro (UNAM Ensenada).

Breakfast was included with our hotel, but we still were issued a bill for $0 ($ = Colombian pesos) every morning. Fortunately, someone had a 0 EUR note with which to pay.

In the lobby, with Rodrigo, Keith Nowicki (SwRI-Boulder), Kai Getrost (amateur, Cleveland, OH), and Ted Blank (IOTA, Phoenix).

We spent the part of the morning at the US Embassy, briefing them on what were were doing and getting various briefings from them about security. Colombia is a much different country than it was 20 years ago, and while it is not crime-free, it is much safer than its reputation. We still wanted to be careful, and spent a lot of time investigating the security of regions we were headed. Rodrigo and Keith talked frequently with SwRI and local groups.

Meanwhile, Rodrigo has been working with the local Colombian meteorological group to get us daily local weather predictions for Friday night, for all of our potential sites. We don't know at this point where we'll go, but these sites are likely candidates.

At the same time, we start looking at areas around the occultation paths to plan potential sites. The lines are spaced roughly every 5 km, so we want to find a site as close to a line as possible. The groups in Senegal have a similar map based on the same predictions, so that our observations will interleave appropriately with theirs.

After a morning of planning, we head out to lunch for our first Colombian meal. Walking back we get pelted by some some nice Colombian summer rain. Bogota is living up to its reputation of cold and wet!

Time to meet with the locals! We head over the local university (Universidad Nacional de Colombia - Bogota), where we are met by Giovanni Pinzon. With him are Rodrigo, Ted, Aart, and Kai.

Rodrigo talks over the observing plan. Planetary science is pretty new to Colombia, so he give a lot of background on what we're doing and why. Rodrigo is himself from Chile, and represents about half of the Chilean base of planetary scientists!

At the Observatorio, ___, Giovanni, Sergio, and Andres Molina listen to Rodrigo.

At the Observatorio, Rodrigo talks occultations.

With the Colombian locals, we start making up potential teams. Each of the paths has a unique number (e.g., Kai and I were on path I-60-61).

More occultations discussion in the night.

Colombian telescopes must have some of the best water-proofing in the world...

As we were leaving, Diana sent this photo (which is not us -- it's from an amateur meeting a few years ago). "This shows exactly what Colombian astronomy in the rainy season is like!" (Photo by ASASAC.)

Meanwhile, Raul Joya sets up their large dobsonian. Hey, at least it's dry in that parking garage. (Photo by Raul Joya.)

Our telescopes were delayed clearing customs, so they're not here yet. But they're anticipated tomorrow, and we'll need vehicles to pick them up from the warehouse. We've headed back to the airport to rent the largest cars we can find, as Ted, Kai, and Aart stand near the Avis rental booth.

Renting from Avis is a pretty manual process -- check out that hand-written inventory list.

The Avis booth is situated at the main terminal, but it actually doesn't even have any electric power. "We just keep a 12V lead-acid battery down here. I charge it up every night, and I run the laptop and printer off of it."

Cost of a four-day rental: 3 million pesos!

With our cars now set, we head over to the US Embasssy warehouse to pick up our telescopes, which have just arrived into Bogota. After the telescopes are loaded up, we headed back to the Observatory to meet up with the local observers, and set up our equipment for a test run.

No photos of the warehouse, but it was a vast space, many layers high, stacked primarily with household furniture for employees of the US government (State Department, etc). Rows and rows of dining room tables, refrigerators, and end-tables. And then in the corner, locked in a cage, a big pallet of telescopes! My family and I have lived in State Department housing for most of the last decade, so I'm quite familiar with their furniture, but I'd never had a reason to visit one of their warehouses before today.

Aart hauls that optical tube assembly ('OTA') into the observatory.

Check out the mount on this telescope at the Observatorio. That's a polar mount, sited at 4 degrees north latitude.

This means that the North Star -- Polaris -- is just a few degrees above the horizon. The geometry of observing near the equator actually made it challenging for some of the local groups in Colombia to set up for the MU69 occultation. Polaris is really hard to find so close to the horizon due to trees and anything else that may be in the way. An Alt-Az mount can be a lot more flexible in terms of choosing calibration stars.

On astronomy exams I have put test questions along the lines of "Where is this telescope from?", which you can answer knowing that the latitude is necessarily welded into the telescope's structure. But for whatever reason (tropical weather?), it's rare to see a mount with this small a polar angle... I'd certainly never seen it before.

Paul and Keith have set up their telescope. Yes, we are setting up inside because it's not quite good enough to venture outdoors yet.

Ted and Rodrigo with their telescope (and me at the bottom). Looks like telescope T22's main 16-inch mirror has survived shipping this time! This was one of the ones that had a dislodged primary during the South Africa expedition last year.

We sit down for some tasty Colombian food near the university.

Giovanni: "OK, in Colombia there is just one question they'll ask you when you order: 'Beef, or Chicken?'"

We've got tasty meals of beef and/or chicken here. That's some blackberry juice (mora) as well. And yes, we got arepas (like mini-tortillas) and plantains as well, even without asking.

Kai Getrost, Keith Nowicki, and Rodrigo Levia.

Giovanni Pinzon and Ted Blank discuss occultations.

I'm sure someone understands this cartoon left on our table, but it isn't me!

Jaime Garzon (Bogotan comedian and journalist) and Che Guevara, over the campus of the university in Bogota.

"Tocame para escibir," ('touch me to write') says the graffito.

Our local collaborators in Bogota! Photo by Alfonso Caycedo.

Back at the university, the local Colombians start setting up their telescopes. Here Raul Joya (U. Sergio Arboleda, Bogota) starts on one of their 14-inch Celestrons.

Karina Sepulveda unseals the packing crate for one of the 14-inch Celestron mounts. She teaches astronomy at a local K-12 school, Collegio Abraham Maslow, and they have sent their telescope along for the occultation.

Alfonso Caycedo runs the Collegio Abraham Maslow that has sent the telescope. "Oh look -- it's nothing but clothes inside!" (But dig deeper and he'll find a mount in that box.)

Mounting the 14" Celestron tube on the mount. This telescopes has come out of the observatory at Collegio Abraham Maslow. "It's the first time it's ever left our dome!" says their director Alfonso. From left, Andres Molina, Raul Joya, and Giovanni Gonzalez lift it up. It is really heavy!

Karina Sepulveda and Raul Joya bolt the telescope into the mount.

Gotta put on those heavy counterweights!

Keith Nowicki is excited to continue to iterate with SwRI on local security.

Ted Blank is almost ready to observe the ceiling!

Our cheap Dobsonian telescopes have a lot of particle board and plastic, and they bolt together like an IKEA dresser. They don't have nearly the durability or stability of the Celestrons. They are, however, a whole lot easier to carry, and to ship around the world.

As Ted Blank looks over the telescopes, Rodrigo Leiva goes through the fun task of updating all of the laptops. We want to make sure that the software, CCD firmware, and observation profiles are set properly, and match what the Senegalese group is using.

Rodrigo and Ted work on CCD software setup.

Here's Diana Rojas, who runs the the Asociacion de Astronomia de Colombia (ASASAC).

"This is the Pablo Escobar telescope... his personal telescope. It's about 30 years old. He had it so he could see who was approaching from a really long way away. After he was killed, it sat in the office of his lawyer for over a decade. Eventually the lawyer decided he didn't need it, so it ended up at the Observatorio here in Bogota. It has a new mount and the optics are still excellent, so we're going use it to observe the occultation on Friday."

Aart reads up on the 'Plankton' -- the consistent (yet ever-changing!) plan for the teams to set up and observe the occultation. These same telescopes have been used several times before: first in South Africa in 2017, then to Argentina, back to Boulder for check-out and testing, and now to Colombia. Each one weighs about 100 lbs, plus another 200 lbs for the four large crates in which they travel.

In Colombia we had nine total sites:

• Three 16-inch portable SkyWatcher dobsonians (SwRI -- our group)
• Four 14-inch portable Celestrons
• One more portable dobsonian
• Two fixed sites near Medellin -- 13-inch and 25-inch.

Raul Joya puts an eyepiece onto the Pablo Escobar telescope, as Hermando Rojas observes.

Kai Getrost and Joel Castro check out the finder charts. They're updated a little bit from last summer, but the area of the sky is almost the same: MU69's orbital period is almost 300 years, so it moves slowly across the sky.

Rodrigo finishes up some Colombian snacks. On the board you can see a list of observing teams on the left, and some exposure time calculations on the right. All of the SwRI telescopes are identical (16-inch f/3.5), but the local scopes have a variety of sizes, so we wanted to work out consistent exposures so the data could be merged well.

And check it out! The skies have cleared for the first time, so we decide to move outside. Rodrigo and Ted set up their telescope, while Alfonso Vicinni (ASASAC) looks on.

Setting up the 14" outside. That's a polar mount, and they are aligning it on the north star, Polaris, which is a little tricky on the equator! Santiago Vanegas (U. Nacional) is at the center, with the Mexican group: Joel (seated) and Sergio.

Kai Getrost is on the target field! Looks like the other group is pointed in the same place as well.

We're pointed on the right field in Sagittarius for the occultation. Kai (in blue) stands next to our telescope. With the laser is Alfonso, and Karina is to his right. Alfonso is pointing out the location of the star Nunki -- part of the handle of the teapot, and the closest bright star to MU69. Easy to see (2nd magnitude), even under bright floodlights!

Rodrigo, Alfonso, and Diana at the practice session.

Rodrigo, Giovanni Gonzalez, Alfonso Caycedo, and an interested passerby (a U Nacional pharmacy student) check out the CCD images of the field.

Across the street, a big crowd gets the C-14 going. That's Alfonso Caycedo, Francisco Tamayo (UNAM), Raul Joya (ASASAC), Charles Triana, and Giovanni Gonzalez.

Karina Sepulveda is aligning at the finder, as everyone watches from the laptop. From left: Adolfo Viana (ASASAC), Kay Getrost, Francisco Tamayo (sitting), Raul Joya, Giovanni ___, and ___.

Meanwhile, Kataline (U. Nacional) and Andres Molina have got the Pablo Escobar telescope up and running.

After two days of prep work in Bogota, it's time to head to the occultation path. It's now Wednesday morning, and we're at about T-2.5 days until the occultation on Friday evening. We've been monitoring the weather constantly. There's no one ideal place to go, so we split up: the local Colombian observers are headed eastward to Barbosa and Suaita, while the six of us and one local will head west, to the area around Puerto Boyaca. By spreading out, we hedge our bets and improve the odds of getting good data.

Colombia is pretty rural and mountainous, so we can't just go anywhere: we are limited to observe where the occultation path (solid black lines) intersect cities and major roads.

And we're on the road!

Kai makes friends with a local gas-station perrito. We're dropping in elevation fast here: from Bogota we go from 8600' elevation to about 100', as we drop off of the high Colombian plateau into the low river valley. Diana warned us: "It's going to be extremely hot, with a lot of mosquitos. You will all get eaten alive, I am sure of it!"

A brief stop in Guaduas, halfway on our trip. It's a beautiful old town.

We didn't think we were on a tourist circuit at all, but it turns out that Guaduas is a pretty famous old city, and one of the endpoints of the 'Ruta del Sol' which sees a lot of tourism. A pair of guides come up to us and show us how the scene we see here is actually on the back of the 10,000 peso note! (But the church is missing from the engraving -- it's from 1870 and thus too new to be on the bill.)

What would a Zocalo be without pigeons?

Photo by Ted Blank, who has just arrived into town.

And they all fly!

Diana has caught up with us, and we enjoy another Colombian plato del dia ("Beef or chicken?"). Oh, and some soup! Every classic Colombian meal starts with soup.

On the road to Puerto Boyaca, I was really excited to see this sign, since I figured that Entrada y salida de volquetas meant there were anteaters coming on and off the road! As it turns out, volquetas actually means truck, not anteater. Oh well.

Sloths!!

And the awesome road signs of Colombian wildlife kept on coming!

Colombian trucks weren't quite as overloaded as they could be, but there were some extra passengers here and there.

And we've all made it to Puerto Boyaca, our home base for the next four days! You can see a telescope tube in the back of the vehicle. Time to find a hotel with telescope-safe parking!

Puerto Boyaca is a small town -- maybe a population of 20,000. Many Colombian towns are built around a main square, which gives a nice center to the downtown, but our square was unfortunately closed for reconstruction.

Up until 10 years ago, Puerto Boyaca was a hotbed of activity due to guerillas, cartels, and paramilitiaries. Diana tells us that in that time, the entrance to the town was essentially on lockdown outside of daytime hours -- no one could come in or out.

Birds outside the hotel.

Aart and Keith bring equipment into the hotel.

This makes our hotel seem a lot more fancy than it really was! We were in pretty basic window-less rooms. But it did have what we needed: covered parking, and a nearby bakery.

Aart, Keith, and Diana discuss logistics.

And in the hotel lobby, we do our regular weather check, comparing all the predictions from different weather sources to try to predict what was going to happen on Friday. If it was 100% clear or 100% cloudy, it would be obvious what to do. But we were always in that middle range.

At a local bakery, I load up on Colombiana, a tasty brown creme-soda beverage.

Our daily morning breakfast at a different local bakery: huevos, tamales, arepas, and a lot of fresh juice.

And more breakfast: soup (with potatoes and meat), a huge tamale, and eggs and arepas with fresh cheese. And coffee!

Keith tells the story of how he danced 100 hours during a 10-day trip to Cuba.

And for dinner, check it out: that's chicken and beef cooking on the grill for us!

Me: So, what do vegetarians do in Colombia? What do they eat?

Diana: It's hard. Not very much!

Oh look -- it's more meat!

Around the corner from our hotel was a fantastic raw vegetable market. 'Raw' because there wasn't much sorting done: it looks like every tomato grown gets thrown into the same bin. 'Fantastic' because there were so many species of fruit that I couldn't identify!

Passion fruit and guava!

Kai inspects those guavas and squash.

Kai and I are out hunting for spots. Our goal is to find a site that's accessible, safe, and dark, and within 100 meters of our assigned path. Here's the first one. A nice road, and it's just off the highway.

But we go a short distance, and come upon a common nemesis: a closed gate, with no one obvious around to talk to.

We keep poking around, and find a few moderately OK sites, though nothing great. But we have the full day for scouting, so I suggest we head to the other side of the river. It turns out to be a long way: the river is wide and fast, so there are not many bridges on it, and there's a lot of back-tracking to get across. Once we do so, we hit a gravel road, and then we start heading through the land of oil derricks. It was looking pretty bad, but we didn't have a better plan so we continued on the road and hoped for the best.

Interestingly, Kai realized later that Pablo Escobar's main residence -- Hacienda Napoles -- was just a few kilometers from here. He left a cadre of hippos and other animals, and it has now been turned into a state-run water park.

Then the oil derricks give way to cattle plantations -- a lot of cows, and a ton of intensely beautiful rolling green fields of thick grass.

Some interesting geology here: check out that terracing above the cows. At first I thought it was some sort of agricultural thing (like ride paddies that had been built), but these terraces were everywhere, making me think it's probably sedimentary?

We pass by dozens of large cattle plantations, and thousands of cows, but see almost no one.

A beautiful iguana! I got an inch closer, and then it raced away, fast!

Eventually we get to our line, and are astonished to find a farmhouse sitting right where we want, with kids out front front. These are virtually the only people outside we've seen all day.

I sharpen up my Spanish (dormant since living in Mexico City a decade ago!), and chat up the locals. They take us back behind their sheds and showed us the train track, from which there's a decent view of the southeast sky.

"But you should talk with Don Reynaldo up the hill. It's very nice up there, and you can see everything from his place!"

We got back in the truck and drove up the hill to find Don Reynaldo sitting on a bench in front of his farmhouse. Kai and I sat down with him. He liked the idea of having a telescope set up, and took us over to this beautiful hilltop. It had a great view, but turned out to be a bit too far to lug our equipment. We ended up in the second-best place - a cattle feeding station on a closer hill, with a nice south-facing view.

Reynaldo manages the ranch and has worked here for 30 years, taking care of 700 cows! The owner of the farm lives in Medellin. He comes occasionally to check on it -- last time was six years ago.

And here's our observing site! Reynaldo is marking off a space for us to set up the telescope.

We had set out in the morning to scout for sites, and didn't bring all our gear with us. But now it's getting late, and we definitely want to have a practice night at our site before the event. So we get back in our truck and do the four-hour round-trip drive, pick up our laptop, and then return to the site before sunset.

We've been monitoring the weather continually. So far it looks pretty good for tonight (Thursday), though a little sketchy for Friday.

Evening comes and we set up the telescope. The clouds open up and we have a fantastic sky. This shot is taken to the east, as Mars is rising (the huge orange blob). Above that is Sagittarius, and then Ultima Thule is right at the top. Nunki -- in the handle of the teapot -- is the closest bright star, and the one we use as a pointing reference. You can see the headlamp trails of Kai and I going back and forth to the car.

Kat sets up the telescope. To the right is the beautiful Rio Magdalena. And the glow just above the river? That's not city lights, but lightning starting to move in.

We're joined by Don Reynaldo and his daughter (sitting in the chairs at the left). They're watching us set up and work!

Kai sets up for our occultation test-run. The idea here is that we will take exactly the same dataset at the real event tomorrow: same exposure, same pointing, same field.

You can see the CCD camera (with cable) sticking out of the eyepiece port on the telescope's left. Kai is finishing up the test observation -- a 20-minute dry run on the real field. The clouds are coming in, but we managed to keep centered on the clear field the whole time.

Looking to the south, the lightning and clouds are building up. Below them... hndreds and hundreds of fireflies! I love this pic: fire above, fire in the middle, and fire below.

The clouds were rolling in, but we managed to avoid the rain. The planets were bright and beautiful. We set up the telescope with an eyepice and gave a tour of the sky to Reynaldo and his two kids, looking at Mars, Jupiter, and Saturn. By that point we were pretty clouded over, so we packed up and started the two-hour drive back to the hotel.

Mid-way through the drive the rain suddenly hit us, and we got slammed! It was a truly torrential storm. Lots of trees were downed onto the highway, and we were driving through a nearly continuous midnight sky of blue and purple lightning. It was awesome.

Good to see that local TV reporters in Colombia reporting on flooding go through the same antics they do in the US!

This particular broadcast related to a different storm than ours, on the far east side of the country.

But Puerto Boyaca got hit pretty hard from the storm as well, and the local mayor was interviewed about it. Several of our group had been meeting with him the day before, in order to secure permission or get access to sites. He ended up being a big help to us in finding a farm for Aart and Keith to observe from. That was the day before -- and today, he's dealing with mega-flooding.

Meanwhile, while Kai and I were off scouting, here's the site that Rodrigo and Ted found for their occultation line. It's a large Colombian resort and restaurant, right on the highway, packed with 15 loaded tour buses. But despite the day-use, the attached hotel was completely empty, so at night, it was dark!

Right here is the actual site from which Rodrigo and Ted observed: they set up their telescope next to the pool, observed, and then had a 20-foot walk back to bed at the end of the night. We joined them for breakfast to talk about our experiences for the dress rehearsal.

The weather for the event night looks only slightly different than it has all week. Looking globally, it appears that the exact same storm that's hitting us in Colombia is also on top of of colleagues in Senegal!

Rodrigo does some testing before setting up at their pool-side occultation site. Bring on the margaritas! Photo by Ted Blank.

Weather's not looking too good for any of our sites in the west. Hmm -- large rain, peaking at 8 PM Friday night.

Looks like the weather at the eastern sites will be a bit better than ours... a bit of hope in Sogamoso??

Field trip: Meanwhile, far away from us on the eastern side, Alfonso Caycedo's group is ready to observe on their line. (Photo by Alfonso.)

And, on the other side of the country outside of Medellin, the team at San Vicente de la Loma is getting set up. at their fixed site. (Photo by Lam Wu.)

Back to us: time for one more drive out to our site! The Colombian terrain here is really unique and beautiful.

This local farmer is hauling a load of potatoes.

So many beatiful cows.

And we're just about to our occultation site. We'll set up the telescope on the top of this gentle hill.

The sun is starting to set. Nominally, it would be time to set up the telescope. But it looks like our site is being used by other occupants! We can fix that problem adequately (Don Reynaldo showed us how to shoo away the cows). But... with clouds like this, it's just not worth settting up the telescope and risking the rain. We'll sit tight and see if things improve.

Trying to wait out the clouds, we talk with our host family. His son (also named Reynaldo) is in 5th grade and likes science, and Spanish. He takes the school bus every day.

I've brought a small drone with me, and I send it up to check out the Colombian countryside. (Yes, legal in Colombia -- I checked it out beforehand!) Once it comes back, I ask the kids if they want to fly. Check out the video!

Kids flying the drone!

Natives come out to investigate us.

Sun sets. Clouds stay put.

Not having anything better to do, I keep taking photos of cows.

Oh look! It's another cow!

7:40 PM. 45 minutes before the event, there was a clearing, and we could definitely see things opening up. We unloaded the telescope from the truck, set it up in record time, and aligned on Arcturus. We needed a second star to align to, so we waited for Antares to come back. It never did, and then every star that we'd seen slowly went away.

We were at T-15 minutes to the event, and no stars. We saw our target field in Sagittarius once -- where both MU69 and our target star were hiding -- but then it was gone.

And, time to check Slack for the updates from some of our colleagues...

And then... back to Bogota. We drive back on Saturday, and then have Sunday free. I'd heard for years about the city's Ciclovia, where Bogota shuts down some 100 km of roads every Sunday, open only for cycling. (Mexico City did a very similar Cicloton every Sunday, whiech we often rode when we lived there.) Kai, Ted, and I rent bikes and head out. Paula of Biking Bogota has set us up with bikes and a map.

Bogota is high, cloudy, and beautiful. Check out those mountains!

Ted bikes past some nice artwork.

There are tens of thousands of bikers out. It's not fancy -- just mellow and easy. Lots of kids, and lots of dogs.

Ted and Kai.

Kai and I wander around downtown, in the Candelaria historic area. I eat everything I can buy, including this concotion of green mangos and lime.

More tasty beverages! This one is a stew of passionfruit and guava.

Check out those insects! These are gigantic dried ants, sold as a tasty snack.

And obletas -- thin wafers filled with caramel and fruit.

Monday morning, we packed up the telescopes and got them ready for shipping back to the US. Diana had been telling us about one of her favorite places near Bogota -- a large underground cathedral made of salt outside of Zipaquira. Sure enough! This is the main hall, and it's about 900 feet underground. The walls are made of more-or-less pure salt. It's really spectacular. The cathedral is commonly called one of the major achievements of modern Colombian architecture.

It's all carved from natural halite, the seams of which you can see in the walls and ceiling. Not surprisingly, it hosts the world's largest underground crucifix.

Kai checks out one of the 15 large 'stations of the cross' -- carved into salt -- at the underground cathedral.