Would it surprise you to learn that the largest building in Kentucky is not, in fact, a building but is instead a massive cavern? Well, friends, it is! And it’s called the Louisville Mega Cavern. After roaming the tunnels below the streets of Cincinnati during our summer road trip, we headed south to spend a couple days in Louisville and took an electric bike tour throughout the Louisville Mega Cavern’s 110 acres!

About the Louisville Mega Cavern

From 1932 to 1973, miners blasted and dug out limestone underneath the city of Louisville, creating the cavern that is the Louisville Mega Cavern today. Some 4 million cubic tons of limestone were mined out over those four decades and used for various highway and interstate projects in the surrounding areas.

In 1973, mining regulations changed in Louisville, stating that you couldn’t use dynamite for mining any longer unless you also owned the land that sat above your mine (seems smart!). The mining company did NOT own the land above the mine nor could it afford to buy it, and therefore the mine had to close its doors.

The mine sat abandoned for about 15 years until 1989. Locals would go down into the mine and get up to no good, and so the city decided to put it up for auction. The current owners of the Louisville Mega Cavern (and two other investors) bought the mine for the bargain price of $2.3 million. 

And…turned it into an entertainment venue! In addition to the e-bike tour we did, they have zip lining, a ropes course, a tram that takes guests on a tour throughout the cavern, and a 320,000 square foot bike park with 45 trails. And all of this is situated below ground, underneath the Louisville Zoo and all ten lanes of I-264 to be exact!

In addition to the fun stuff happening through Louisville Mega Cavern, Louisville Underground operates the business side of the cavern, including commercial storage, vault storage, food-grade storage, RV and boat storage, and more. The cavern is also used for storing tons of road salt for that pesky winter weather. 

In total, there are more than 20 businesses operating from within the Mega Cavern, and Louisville Underground is trying to entice even more businesses to set up shop inside. Part of the appeal is the low utility costs since the cavern stays around 58 degrees year-round. And with only four entrances that are all clustered together, it’s a pretty secure space! 

But we were not there to rent office space – we were there to have some fun! And we were ready to get started as soon as we set foot inside the cavern. When you walk into the lobby, you’re only seeing a small portion of the cavern, but it immediately fills you with a sense of awe. It truly is MEGA!

E-Bike Tour in the Louisville Mega Cavern

We chose the e-bike tour primarily because neither of us had ever been on an e-bike before, and we thought it might be fun to try something new. Also, this tour travels through about 65% of the cavern’s interior, taking you into more spaces of the cavern than any of their other experiences. We figured it would give us the best opportunity to see as much as possible during our visit.

Our tour guide, Trenton, met us at the check-in desk and took us out to where the e-bikes are stored. We each got a helmet with lights and a reflective vest which, according to Trenton, would also help to “keep the mud off of us”. 

What?!?!? 

Yeah, I must have missed that bit of fine print, folks. And we definitely got fairly muddy, to the point where I had to get wet paper towels in the ladies’ room afterward to wipe my legs off. Don’t wear clothes or shoes you don’t want to have ruined! (And, as Trenton advised, don’t freak out and wreck your bike if you get mud on your face!)

Trenton gave us a quick demo on how to turn the bikes on and how to operate them. It’s pretty straightforward. You don’t need to pedal unless you want to, and let’s be honest, I didn’t want to, so I just used the throttle the whole time! They’re fat-tire bikes, too, so they’re very stable but also very heavy. Forget about pedaling and just enjoy the ride!

There were only three of us on the tour, and the e-bike tour size is actually capped at four, which is really nice. We assumed there would be 20 of us all getting in each other’s way, but with just three of us, we had plenty of room to spread out. After Trenton watched us all take a few laps as we got used to the bikes, we headed off into the cavern!

Trenton explained that the miners who had carved out the Mega Cavern used a room and pillar method of mining, which is basically exactly what it sounds like. There are big open spaces (rooms) and surrounding them are rows of pillars, which were left behind to support the ground above the cavern. 

Apparently, there are five times the number of pillars in the Mega Cavern than what is actually needed to support the earth above it, so it’s pretty sturdy down there! In total, there are 223 pillars in the cavern, number one being the first and oldest and number 223 being the last and newest pillar. 223 is all the way in the deepest reaches of the cavern, and that was our ultimate destination.

Before getting there, though, we made a couple stops on the way. First, we stopped at what Trenton called a “water wall”. There is water seeping into the Mega Cavern all the time, and they have to pump out around 55,000 gallons a day to keep things as dry as possible down there. We got off our bikes and were able to walk over and touch the wall where the water was running over it. 

This is also one of the only places where creatures live in the cavern, and we spotted a couple of the little guys ourselves. They’re red cave salamanders, and one of them wasn’t red at all! It was white, having lost some of its pigmentation from hanging out in the dark Mega Cavern for so long.

We continued riding deeper into the cavern, and at another stop, Trenton explained that although the cavern used to be about 120 feet deep back in its mining days, it’s only around 30 feet deep now. That’s primarily due to Mother Earth Recycling bringing in tons of inorganic material, which was used to fill in the cavern and raise the floor up to the level you see now (and hence why we were able to ride bikes on it!)

At our next stop, we got a glimpse of some of the people zip lining inside the cavern. Since the Louisville Mega Cavern is home to the world’s only fully underground zip line course, they’re also holders of a couple world records.

First, they hold the record for the world’s longest underground suspension bridge at 180 feet long. When the zip liners walk across it to the next platform, they’re standing at about 100 feet above the bottom of the cavern when they hit the halfway point on the bridge. Their second world record is for the world’s longest underground zip line, with the longest traveling 900 feet down through the longest corridor of the cavern.

And surprisingly, though we could hear people zipping through along the wires, we didn’t hear any of them screaming! I most definitely would have been, especially on that 900 foot-long line! So really, aside from the occasional sounds of zip liners sliding by, the cavern is eerily quiet (and dark!), especially as you progress deeper into it.

Which we did! On our way to the next stop, we traveled along a nice straight, flat stretch, free of mud and rocks. We were able to test out the speed on the bikes, and I chickened out at around 15 mph because it was just far too dark to tell what was in front of us, even with our bike and helmet lights!

We made a couple more stops, and Trenton pointed out some of the other interesting features within the cavern, including some very cool wild mushrooms that manage to grow inside, as well as some old carts and machinery that had been left behind by the mining company when they abandoned the cavern.

What came next, though, was especially fascinating. We learned that during the Cold War, the Mega Cavern had actually been designated as a fallout shelter, and plans had been put in place to house 50,000 people in the event of a nuclear threat. This would have made the Mega Cavern the largest fallout shelter in the state of Kentucky!

The cavern was selected for its size and for the fact that water naturally makes its way inside through underground streams and rivers. The water in the cavern is 98% pure, and the idea was that filtration systems could be put in place to purify it even further (not sure at what point radiation would have started to seep into the water table or if that’s even a thing, but it seemed like this would probably become problematic at some point?)

Projections at the time indicated that 50,000 people would have been able to survive within the cavern for up to two years. Back then, the cavern was still being used as a mine and so it was still at its depth of 120 feet. Nowadays, 50,000 people would have way less time down there with the floor of the cavern having been raised up to its current depth. (And in case you were wondering, Col. Sanders was apparently one of the 50,000 people who was on that list!)

As we moved even deeper into the cavern, we came to what was my favorite stop on the tour. There are four underground ponds inside the cavern, and we got to walk down to see one! At the banks of the pond, we were standing at the cavern’s original depth of 120 feet (and about 260 feet below ground!) One of the walls down there was covered in names, scratched on with a rock. Trenton told us we could add ours if we wanted to, so naturally, we did!

After the pond, we biked on to pillar 223 in the deepest part of the cavern, and then, sadly, started our way back to the entrance. We thought the surprises were over but then suddenly – Christmas lights appeared! It turns out that the Mega Cavern is also home to an event called Lights Under Louisville, held every year around the holidays.

Christmas light displays are set up all throughout the cavern, and people can come in (with their own cars!) and drive throughout the cavern to enjoy the displays. Trenton mentioned it’s a hugely popular event, often backing up the interstate for hours at a time! Personally, I think it would just be really cool to say I drove my car inside a cavern, so the Christmas light display would just be an added bonus at that point!

And with that, we continued back to the entrance and wrapped up the tour. We had an absolute blast, and my husband declared this his favorite activity of our entire weeklong road trip (and also really, really wants an e-bike now!)

If you find yourself in Louisville sometime soon, I would highly recommend checking out the Mega Cavern and consider making a whole day out of it so you can try out the zip lining, too!

Have you ever been to the Louisville Mega Cavern? Let me know what you thought the first time you visited!

And if you’re like us and enjoy exploring caves, caverns, and tunnels, check out some of the other underground experiences we’ve enjoyed.

Plan Your Own Visit

Where to Go

• Louisville Mega Cavern: 1841 Taylor Ave, Louisville, KY 40213

When to Go

• The Louisville Mega Cavern is open 7 days a week. Check their website for specific times for each of their attractions.

Tips for Visiting

• The e-bike tour is limited to four riders, so if you’re a larger group, you’ll need to split up. Do book in advance, though, because these tours sell out quickly due to their smaller size.
• The e-bikes do come in different sizes, but they suggest a minimum height of 5’-2” for riders to be able to safely and comfortably ride the bikes. Also, children under the age of 12 are not permitted on this tour.
• If you’re doing the e-bike tour, you WILL get muddy. Wear shoes and clothing that you won’t mind getting covered in mud. They’ll give you a reflective smock to wear, but it won’t help your shoes or legs to stay clean! It’s wetter in the summertime, too, so maybe consider going in the fall for a less muddy experience.
• And though it should go without saying, even though these are electric bikes, you still need to know how to ride a bike before signing up for this tour. You really don’t need to pedal – you can let the bike do all the work – but you need to know how to balance on a bike, use the brakes, etc.
• The cavern stays around 58 degrees year-round, so if you visit in the summertime and you’re wearing shorts or a tank top, don’t forget to bring a hoodie or sweater with you. 
• You’ll need to sign a waiver to do any of the activities at the Mega Cavern. Save some time on the day you arrive and do your waiver online in advance. You should receive a link to it after you get your confirmation email or you can find it online.