Onondaga Cave State Park

Totally a hidden treasure and an amazing Cave! Must do the tour ($ 15 for adults). Really cool formations that rival Mammoth and Carlsbad Cavern, which I’ve visited and would say Onanadaga was very much on par with them. Our guide Nick was informative.
The Park itself also has a nice, clean campground $ 13/​night with showers and firepits. Several hikes around the state park were great also. Lots of spiders and ticks, so make sure to bring appropriate long pants, DEET and a hearty constitution, but otherwise reminescense of hikes around New England with lots of bedrock/​limestone/​dolomite cliffs and mossy trees. We did the Vilander, Deer Run, and Oak Ridge and highly recommend them all. Deer Run and Oak Ridge depart from the campground. Only 80 miles from St. Louis and ~4hrs from KC, this State Park is definitely doable for a weekend. Fun float trips on the Meramac are very close also.

One of my favorite day-​trip destinations. While I have yet to take a cave tour, the hiking is enough to keep me coming back. It’s a beautiful area with long trails, challenging inclines, and some scenic streams and ponds.
The trails could be marked a bit more clearly, but I made it out alive so it can’t be too bad.
When you’re on the blue trail, be sure to look for turtles perched on branches over the water. I love those little guys.
If you’ve got a weekend day free, pack up the car, take the drive and spend half a day here. It’ll cure what ails you.

this place was so much fun!
my friends and i came here for a cave tour. the tour guide was friendly and informative. she didn’t know EVERYTHING but that was ok.
i like going into caves and onondaga caves did not disappoint! there were concrete steps and low ceilings all over the cave. my bf is pretty tall and the tour guide kept on teasing him about potentially hitting his head. he crabbed walked under the low points and was safe!
anyway, i agree with Tom J in the way this place was very nicely designed for the tourists. we would walk somewhere, the tour guide would press a button, the formations would light up, and she’d talk at us for a bit. then the lights would go off, we’d keep walking, and rinse and repeat.
the cave tour is cash only (if i remember correctly) so bring cash just in case! and bring some pennies and quarters for those crushed penny souvenirs!

We took a tour here last week. You wouldn’t know it based on advertising or word of mouth, but I say this is a major attraction for the St. Louis area — everyone who lives here should see make it a point to see this cave. They are now closed until springtime (mid April — TBA).
Tours of this cave began shortly after it’s «discovery» in the late 1800’s. It was a big attraction at the time of the 1904 World’s Fair. Before people began to fully understand conservation of caves, they poured a concrete path, added electric lights and banisters. Although environmentalists might consider this a shame, it works out pretty well for us tourists, as there is excellent lighting of all the features. The tour leaves the two major highlights — the queen’s veil and the lily pad room — to the end, but along the way there are pretty impressive cave formations all around. If you’ve never been to a cave, this is an excellent place to start. A couple years back, we toured Fisher Cave in Meramec State Park. It’s also very cool, but not nearly as impressive (and no electricity or paths).
We brought our 5 year-​old and she walked the entire tour with not one complaint. We saw maybe a dozen bats, mostly flying by when we spooked them. The tour guide was very fond of the bats, so I think her attitude kept anyone from freaking out.
You might want to read up on Wikipedia before taking the tour — it’s an interesting history. Cost for this season was $ 12 for adults, under 6 free. I think $ 6 for children over 6.
Bottom line: This cave is so under the radar, but should not be. Make plans to take this tour — you won’t regret it.

As far as caves go, it’s far better than Meramec Cavern. However, Meramec Cavern is more commercial than this one (if you’re in to that sort of thing).
The cave tour is two whole hours. DO NOT forget to wear something warm in the cave. It is seriously cold. The formations are awesome and the history of the cave ownership is pretty interesting too.