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Today’s track: Stay or Leave — Dave Matthews and Tim Reynolds

Every day, more than 150,000 people drive over the largest building in Kentucky and have no idea they did it.

It's not a stadium. It's not a warehouse out by the airport. It's under the Watterson Expressway, under about 70% of the Louisville Zoo, 75 to 100 feet down.

Four million square feet. Around 100 acres. Seventeen miles of roads. It stays 58 degrees all year long.

Most of you know it as the place with the underground Christmas lights. Fewer people know it was supposed to save 50,000 lives in a nuclear war.

Let me tell you the story of the Mega Cavern, and then the bigger story of the rock it's carved out of, because that rock explains more about Louisville than almost anything else.

In the 1930s, a man named Ralph Rogers started a company called Louisville Crushed Stone. The story goes he could look at a piece of land and tell you how much rock he could pull out of it.

His timing was perfect. During the Depression, the federal government put people back to work building roads and bridges, and roads and bridges need crushed limestone. Lots of it.

So they dug. For about 42 years, from the early 1930s into the early 1970s, miners blasted limestone out from under this part of Louisville and hauled it off to build roads and bridges across the Midwest. To keep the ground from caving in, they left huge pillars of solid rock standing, some of them 85 to 90 feet tall. Parts of the mine under today's Watterson were dug out before the expressway was even built on top.

When they finally quit in the early '70s, they left behind a giant underground room the size of a small town.

In October 1962, during the Cuban Missile Crisis, the country thought a nuclear war might actually start.

State officials looked at that quarry, a ceiling of solid rock with a lot of dirt on top of it, and made a plan. If the bombs came, roughly 50,000 people would go underground there. There was a list of names, and it was kept secret. One of the later owners has called it the largest civil defense shelter in the country.

Fifty thousand people. That's most of a sold-out L&N Stadium, living in a limestone mine under the zoo.

The bombs never came. The mining kept going for another decade. Then it stopped, and the whole thing just sat there.

From about 1972 to 1989, it was a hole in the ground. A very large, very dark, very empty hole.

In 1989, a man named Jim Lowry and a business partner bought it. Most people saw an abandoned mine. They saw 4 million square feet of space that a tornado can't touch, that never freezes and never bakes, sitting in the middle of a major city with highway access.

So they leased it out as high-security storage. The federal government has rented space down there to keep records. Attorneys have stored sensitive files there. It's run a big recycling operation. Over the years, more than 850,000 truckloads of fill dirt and rock have been hauled in to raise the floor so trucks can drive in and warehouses can be built between the pillars.

Then they got playful. Tram tours started in 2009. Then zip lines, all underground. Then an underground ropes course. In 2015, they opened a 320,000-square-foot underground bike park. And every holiday season for nearly 20 years, Lights Under Louisville has turned the place into a drive-through Christmas show with more than seven million lights. If you’re local, you know the traffic it causes as well. USA Today and other national outlets have called it one of the best holiday light shows in the country.

Louisville Metro and the state of Kentucky classify the Mega Cavern as a building, not a mine. That's why it's the largest building in Kentucky. The ground on top and the space underneath even have separate zoning.

Two properties, stacked on top of each other. A zoo on one floor and a warehouse district on the other.

Oh, and the lowest entrance sits 25 feet above the top of the floodwall. If you read Abe Lincoln Walked on Water, you know why that number matters in this town.

The Mega Cavern is just the most dramatic example. The rock under it is the same rock under almost all of us.

More than half of the rock at the surface in Kentucky is limestone. It's the stuff the Falls of the Ohio are made of, the reason Louisville exists at all (that's the whole story of Right Twice). And once you start looking for it, it shows up everywhere.

It's in your bourbon.

When rainwater soaks down through limestone, the rock filters out iron and adds calcium and magnesium. Iron makes whiskey taste bad and can turn it dark. A University of Kentucky geology professor once put it simply: limestone water is what we had here in the late 1700s, when people started making bourbon.

Louisville Water hooked up its first distillery in 1869. By 1906, it was serving 24 distilleries and 25 breweries. Today, nearly 20 distilleries use Louisville Water. Every time you drink a Louisville bourbon, you're tasting a little bit of the rock under the city. That being said, I don’t really know many people who drink anymore. Considered a level one cancer causing carcinogen….just like hot dogs….

It built the Speed Art Museum.

Before modern Portland cement took over, a lot of America was built with what's called natural cement, made by burning a certain kind of limestone. The magic of it is that it hardens even underwater, which is exactly what you need for canal locks and bridge piers. Louisville had the right rock, right next to a canal.

In 1866, a group of Louisville businessmen bought a local cement company and incorporated it. One of them was James Guthrie, who'd been Secretary of the Treasury and ran the L&N Railroad. Another was Joshua Speed. If that name sounds familiar, it's because Joshua Speed was Abraham Lincoln's best friend.

In 1869 it became the Louisville Cement Company. Joshua's nephew, J.B. Speed, ran it and built a cement mill across the river in Clark County. The town around the mill was renamed Speed, Indiana. It was a company town: the company ran the general store, the hotel and the post office, and owned many of the houses its workers lived in. In 1919, it built a community house with a gym, where the town held dances, movies, school and a baby clinic. Simpler times, maybe better times? Community wise at least… By 1900, according to one local historical society, the Louisville Cement Company was the largest producer of natural cement in the world. Later it invented Brixment, a mortar made specifically for laying brick and block. That plant is still making cement today under a different name.

J.B. Speed also ran Louisville's streetcar company and a telephone company. And after he died, his family set up a foundation in his name that helped found two things you know very well: the Speed Art Museum and the J.B. Speed School of Engineering at UofL.

So let's add it up. The same limestone under our feet built the canal locks, flavors the bourbon, paid for the art museum, endowed the engineering school, and gave us a fallout shelter big enough for 50,000 people.

Not bad for a rock.

Here's where my brain went.

Data centers are the most fought-over buildings in Kentucky right now. Oldham County ran off a $6 billion one planned on farmland and passed a moratorium, which is a temporary ban. Meade County passed an ordinance blocking one. A developer sued Simpson County over its land rules. In this spring's local primaries, data centers were front and center, and one poll found 71% of people oppose a data center near them.

The complaints sound the same everywhere. It's loud. It's a giant windowless box. It eats farmland. And nobody will tell you what's going on.

Now picture it 100 feet underground.

No humming for the neighbors. No box on the skyline. No farmland paved over. A tornado can't touch it. And when the rock holds a steady 58 degrees all year, you spend a lot less money keeping the computers cool.

This isn't science fiction. It's already being done.

In Springfield, Missouri, a company called Bluebird runs a data center 85 feet down inside an old limestone mine. It stays 64 to 68 degrees every single day. The hot air goes straight up a 13-foot shaft. You can't even see it on Google Earth.

In western Pennsylvania, Iron Mountain runs one 220 feet down in an old U.S. Steel limestone mine, and it uses a 100-acre underground lake to help keep the servers cool.

And Louisville almost had one. Back in 2007, a company called StrataSpace announced it had finished site prep on a 500,000-square-foot data center 65 feet underground outside Louisville. The pitch was security, cheap Kentucky power and a constant 59 degrees.

We have the holes. Kentucky is limestone country, and it's full of old mines and caverns.

Underground doesn't fix everything. A data center still needs a massive amount of electricity, and that power still comes in on lines from a power plant somewhere. Depending on how it's cooled, it can still use a lot of water. Those are the parts people worry about on their power bills.

But the noise, the eyesore, the farmland and the fight with the neighbors? A hole in the ground takes care of a lot of that.

If I were a developer, I'd be calling the people who own Kentucky's old mines before I knocked on one more county judge's door. Heat seems to be an issue, would need to repurpose that!

You own more than the grass. When you buy real estate, you're actually buying a bundle of rights: the surface, what's underneath it, and the space above it. Those rights can be split up and sold separately. The Mega Cavern is the most extreme example in the state: a zoo on top, a warehouse district below, zoned separately.

In eastern Kentucky, this used to be a very big deal. During the coal boom, a lot of families signed what were called broad form deeds, which sold the mineral rights under their land while they kept the surface. Years later, coal companies used those deeds to strip-mine land the families still lived on. It got so bad that Kentucky voters passed a constitutional amendment in 1988 to limit them.

In Louisville, it almost never comes up on a normal house. But if you're buying acreage, farmland or commercial land, ask whether the mineral rights were ever split off from the surface. A good title company or real estate attorney checks this. It's one of the reasons title insurance exists.

Know what's under the house. Limestone slowly dissolves in water. That's how you get caves like Mammoth Cave, and it's also how you get sinkholes. Ask your inspector about drainage, foundation cracks and anything soft or sunken in the yard, especially on land and older homes.

And look for the space other people ignore. A dark, empty hole sat under Louisville for 17 years before somebody saw 4 million square feet of opportunity. Most properties have a smaller version of that: the unfinished basement, the detached garage, the carriage house nobody uses, the extra half acre in the back. The value was already there. Somebody just had to see it.

That's what I love about this city. The best stuff is hiding in plain sight. Sometimes it's 100 feet under the road you take to work.

📊 Yesterday's poll: Shotgun or Victorian? Victorian won with 44%. You want the turret. Shotgun, double-barrel, and “whichever one has central air” split the rest at 19% each. Add the shotgun and the double-barrel together, though, and 38% of you picked a shotgun of some kind. And to the central-air crowd: you've clearly been inside a 130-year-old house in August.

Today's poll:

Results in Monday's issue.

🏆 Speaking of value hiding in plain sight, that's the whole idea behind the Top Five. Every morning I screen the entire Louisville MLS and rank the five best deals and the five most ripe for a lowball, with the number I'd offer. One-to-one only. Reply "FIVE."

Grounded,
Rob Bergeron

Owner–Realtor at Award-Winning Winner Realty
Winner Realty: (502) 305-8915
Winner Realty | OffMarket.deals | Property Partner Data Company

Schedule time to discuss your goals, bottlenecks, or whatever’s on your mind — book me here.

The Morning Bergeron daily track playlist

PS: Going into the weekend? Here's every open house in Louisville this weekend, on the Winner Realty site.

PSS: Lights Under Louisville usually opens in early to mid November. Tickets sell out on the busy nights, so if you want a December weekend, book it early.

PSSS: Take some time to relax this weekend!