The Lost Sea in Sweetwater, TN is one experience you really won’t want to miss. This one is unforgettable. If a crystal clear lake, a glass bottom boat, cave flowers, and a guided tour through amazing geologic features sounds like your kind of adventure, then put America’s largest underground lake on your bucket list.
We visited the underground lake and caverns in Tennessee and it did not disappoint. So, get planning! Here’s everything you need to know about the Lost Sea Adventure!
UPDATE JANUARY 2023: The Lost Sea is closed for renovations until February 28, 2023
Always looking for my next adventure, when I heard of the Lost Sea just outside Knoxville, Tennessee, I knew I had to go. I actually keep a running list of all the cool things I want to do and places to go and this one had been on my list for the past couple of years because it is legitimately a crystal clear, cold lake 150 feet underground amongst creepy and cool caverns. An underground lake.
Did it live up to my expectations? Oh yeah, it did.
The Lost Sea Adventure
The Lost Sea is the country’s largest underground lake, which you get to see when you tour the extensive caverns in Sweetwater, TN. And take a boat ride on!
The caverns are huge and have been in use since the days of the Cherokee tribe, who often used the caves to hold councils. Many Cherokee artifacts have been found that point to this history.
During the Civil War, Confederate soldiers mined the caverns for saltpeter, which was used to make gunpowder. Before that, settlers made use of the constant 58-degree temperature in the caves to store their produce.
It wasn’t until 1905 when a 13-year-old boy, Ben Sands, set out to find the rumored lake at the bottom of the caverns. He did end up finding it but no one believed him until decades later when explorers found the same lake. To this day, no one knows how big the lake is. The visible part you see on the tour is 800 feet long by about 200 feet wide and around 75 feet deep. Divers have attempted to explore underground tunnels that protrude from the lake but have not been successful in mapping out how big the lake is.
The majority of the tour is on solid ground amongst the vast cave system that is part of Craighead Caverns. There are all kinds of rare formations throughout the caves that your guide will show you and point out. Many of these formations have taken thousands of years to grow to their current size.
Parts of the caverns have massive rooms and ceilings. If you love geology, you’ll certainly enjoy the tour. The prevalence of the rare “anthodites”, which we learned are called more commonly, “cave flowers” are abundant in these caves. Most caves do not have these anthodites and because of this, these caverns have been designated a Registered National Landmark by the US Department of the Interior.
One particular story that I thought was quite funny was about how one giant room of the cave was a bar and dance hall in 1947. Guests were served moonshine and because of the depth of the caves (or something like that), the effects of the moonshine weren’t felt on the people drinking, which led them to believe they were getting watered-down drinks and drinking all the more moonshine. They would feel the effects of the alcohol once they exited the cave and started up the tunnel to leave. Then it was mayhem. The bar only lasted for all of two months.
I had seen photos of waterfalls in caves before but had never seen one in person till this tour.
Crystal Falls is the name of the small underground waterfall in these caverns that spills from somewhere in the ceiling of the cave onto the formations below. Our guide said it’s the only known source of water coming into the caves. It was super cool and flowed into a small stream next to the lake.
The Boat Tour: A Glass Bottom Boat
So getting to the lake was just as exciting as I pictured. The caves open up into this huge room that is dark except for the lights shining underwater, illuminating the perfectly clear water. I really wanted to grab my kayak or paddleboard and take a ride. They don’t allow that, in case you’re wondering.
The fish all start swimming up to the dock once you reach that area. Now, these are no ordinary fish. These are all Rainbow Trout (no, you cannot go fishing here) that are stocked here every couple of years and are enormous. They are some of the biggest trout you’ll see anywhere. Why? Because they are fed on every single tour that comes into the caverns.
The lake is so clear and untouched that no microbes or algae grow that fish can feast upon. They can’t even breed here. Therefore, they get to live pretty sweet lives being coddled and fed several times a day. Leaning over the boat to get a good look at them was really cool. Part of the boat has a glass bottom so you can view them that way as well.
This was our favorite part of the tour just because it was so unique. Our group was pretty small also and not very talkative so the boat tour was very quiet. In fact, the entire time we were in the caves, it was very silent whenever our guide wasn’t talking. In a world full of constant noise, it was just a different feeling and noticeable.
Wild Cave Tour
If you are up for even more of an adventure, the Lost Sea offers the Wild Cave Tour that includes all of the cool stuff of the normal tour and boat ride plus climbing into undeveloped rooms and seeing all the neat things you don’t get to see on the regular tour.
These tours are for groups like Scouts, camps, churches, or people who just want to explore more. A minimum of 12 spots need to be reserved for this tour and bookings have to happen at least two weeks in advance.
Eating Nearby at Sweetwater Valley Farm
The restaurant and General Store at The Lost Sea wasn’t open when we went so I had to figure out something else for lunch. And that we did.
We went 20 minutes away to Sweetwater Valley Farm, a dairy farm set on rolling green hills, for their grilled cheese sandwiches, milkshakes, and cheese samples. This was one of the best-grilled cheeses and milkshakes I had ever had.
The farm also does tours of their dairy and cheese operations if you wanted to make it a longer day trip to the area. I’m already dreaming of when to go back and get a milkshake.
Things to know about the Lost Sea + tickets
- The tour is a walking tour and you’ll walk about three-quarters of a mile in total with the last quarter mile being all uphill.
- The boat tour is around 15-20 minutes and the total tour time is an hour.
- Some parts of the trail in the cave are slippery so wear proper shoes.
- Kids have to be watched at all times.
- Tickets are $24.95/adult, $14.95/ages 4-12, and kids 3 and under are free.
- The Lost Sea is open all year round except Thanksgiving and Christmas.
- No pets are allowed in the caves and on the tour.
- There is a glass blower, trail, picnic tables, and ice cream shop on the property as well if you want to explore while there.
Homeschool Days at The Lost Sea
Homeschool days are offered every Monday (except holidays) August through May and tickets are at the educational rate of $12/student and $21.95/adult.
The Lost Sea
140 Lost Sea Road, Sweetwater, TN 423.337.6616