I reside in St.louis MO and was wondering how much luck others have exploring the underground of the city,

As long as ive lived here, (my whole life) I've heard stories of underground caves/tunnels with access points all over the city, but no matter how far i search i cant find any info on where they might be, or anything. If anyone does underground exploring in MO I'd love any tips you have for finding locations/ any other insight!

I popped into one of the more prominent drains in the city somewhat recently. It was super easy and sorta neat. I'm not much of a "drain" person, and prefer the older brick lined ones, but it was a good time.

Most of what's findable under St. Louis within practical limitations is CSO (combined sewer overflow) sewers.

Experienced explorers will never offer location info to someone who isn't known trusted because people get injured and then stuff gets sealed up or blown all over the internet which causes more idiots to show up and then someone gets hurt and stuff gets sealed up, or in the case of buildings it gets trashed and then sealed up.

But sewers are relatively easy to find. Water flows downhill. Look at a topo map or wander around until you find the bottoms of valleys. The greater the drainage basin, the larger the pipe or tunnel required to drain it. Might take a while to find access points but with enough persistence you'll figure it out. Waterproof boots are almost always required, waders for deeper water.

Sometimes major sewers don't follow prominent valleys. Sometimes they do. But we all know where stormwater ends up and there are plenty of mapping and imagery tools in this day and age that are useful.

***CSO, particularly in St. Louis is frequently if not usually extremely slippery. You must get either a good pair of ice cleats per person or at least two crappy pairs per person in case the grippy metal things fall off, which did happen to us once about a mile up a St. Louis sewer causing us to immediately turn around and abort our mission to seek a possible lost cave a short distance further, to make sure we made it out before we lost ALL our grippy metal things. (I later found out the info that led me to believe there was a cave lead up that sewer was false so nothing really missed, but this story demonstrates how critical it is to have traction).

Let someone know where you're going or bring friends. I'll admit I don't always do this with the low-risk stuff but a lot of the St. Louis sewers can get risky particularly if you don't have a lot of experience with their specific dangers.

On rare occasions, there are drop shafts with no warning, sometimes it can be 100 feet down to a deep collector sewer. Watch carefully ahead of you if you're walking downstream. Never go somewhere where it's too hard to turn around.

NO DRAINS OR CSO SEWERS WHEN IT RAINS!!! YOU WILL DIE IN A FLASH FLOOD...watch the weather carefully, gotta be under 10% chance of rain and 100% clear radar.