If you’ve ever wondered where in the world the “natural bridge” in Natural Bridge Road comes from, you’re not alone. The answer is tied to Missouri's abundance of caves and the underground world of St. Louis.

It’s a question Joe Light, vice president of the Meramec Valley Grotto and member of the Missouri Speleological Survey, gets asked all the time. Several Curious Louis questioners have wondered the same thing.

Randy, for example, wants to know: Where "exactly" was the natural bridge on Natural Bridge Road?

“It is in north St. Louis at the intersection of 25th and East Hebert … and it’s gone,” said Light. “It’s actually an old cave system and the back half collapsed, exposing a remnant, or a natural bridge. That cave system, if you traced it back far enough up Rocky Branch Creek, it came to Cardinal Spring.”

You can’t see that natural bridge, which consisted of pure limestone, anymore because it has been sewerized and paved over. So there you have it. Natural Bridge Road is indeed named for a natural bridge, which got its start as a cave.

Another question, similar to this one, from David asks: Where is the cave and spring at Cave Springs Road in St. Charles?

Light said he wondered the same question years ago and finally got his question in the hands of MoDOT officials. In the original construction plans for I-70, you can see a cave spring demarcated where the highway was constructed. The cave is filled in, but the water is channeled through a six-inch pipe that empties into a sewer.

The caves of Missouri

There are at least 7,000 caves in Missouri and some of them are right under our feet. The majority of them are located south of the Missouri River, where the geology is more favorable.

Why are there so many caves in Missouri compared to neighboring states like Illinois? Missouri has a preponderance of limestone, which dissolves away relatively quickly when it meets with water, leaving massive voids that make caves.

Kelly Moffitt | St. Louis Public Radio

Light, by day an IT professional, is what you might call a caving enthusiast. The organization he is vice president of, the Meramec Valley Grotto, is one of the most esteemed caving groups in St. Louis, based in Kirkwood. The group meets to explore caves in the region.

“I grew up in a cave-rich section of St. Louis County,” Light said. “That was one strike against me. My parents said they were dangerous: that was two strikes against it. And the movie ‘Goonies’ didn’t help either.”

The largest cave in Missouri is 28 miles long — Crevice Cave in Perry Country. But underground formations are considered caves even at much shorter lengths. In Perry County, there are some 120 miles of mapped caves.

“You’ll have to be on your belly, pushing, scooting and cussing,” Light said. “To be a cave, it has to be 30 feet long and you have to get out of the twilight — it has to get dark.”

The caves of St. Louis

It’s not easy to get into many of the caves under our feet in St. Louis, Light said. Many of them are on private property. If you are given permission by the property’s owner to explore one or go on a trip with a local caving group, you might not be all that pleased with what you find: trash.

“Everything filters down and rolls down the hill into the cave,” he said.

A local group, the Cave Archaeology Investigation and Research Network, however, sometimes is able to find great value in such trash.

“You may see a cave with some trash in it, but they see an incredible wealth of information,” Light said. “If I pick up a rock, it is a rock to me, but they could tell if it has been worked by hands and that could be very valuable.”

(Rachel Lippmann/St. Louis Public Radio) Like most 19th century brewers, Adam Lemp built his business on top of a cave - it provided temperature-controlled storage in the days before artificial refrigeration.

One thing you won’t find? Homeless people, Light said: “I’ve heard that myth, but I’ve never seen it.”

Many of the caves in St. Louis do have a common backstory: They once were used to store beer. German immigrants new to the area needed to find a way to brew and store lagers, which need to be cold. The only option in 1850? Caves.

It was a natural refrigeration option so popular, that big brewers like Anheuser-Busch, Falstaff and Lemp breweries all used them.

In fact, when production eventually outsized caves, immigrants would be put to work chiseling away to make the area bigger.

By 1870 and the advent of artificial refrigeration, however, caves-as-storage were mostly done away with. Light, who has been in some of these beer refrigeration caves, said you can’t find many remnants of that time inside the caves.

Related: Past meets present in hidden world under St. Louis streets

One modern-day St. Louis brewery, Earthbound Beer, is rehabbing the old Cherokee Brewery Co. stock house to serve as its new facility. They’re renovating 45 vertical feet of basement vaults, which were originally caves.

Light said his favorite cave to explore in St. Louis is the Winkelmeyer Cave, which is located near Union Station, and required quite an amount of finagling to get into.

Some caves in St. Louis, like English Cave, have been “gobbled up by urbanization,” Light said, meaning there are no remaining openings to the cave itself.

Want to try caving?

Light suggests anyone who wants to go caving to first try it with a local group, so they can show you the ropes. He adds that you should never go caving with fewer than two other caving partners.

As for equipment, a headlamp or flashlight is a must. For some larger, easier caves, you could wear normal clothes, Light said. In other instances, you might need a wetsuit or other accessories.

The Meramec Valley Grotto has about 60 active members in the St. Louis region, and a couple hundred participants statewide. Here’s a list of other “grottos,” or caving groups located in Missouri. The Missouri Speleological Survey would also be a good resource for those wanting to learn more about caving.

For those not quite ready to do heavy-duty caving yet, there’s also a plethora of caves that are publicly accessible within driving distance of St. Louis. Here are a few to start with:

Onondaga Cave State Park

Meramec Caverns

Cliff Cave Park

Fisher Cave

St. Louis on the Air brings you the stories of St. Louis and the people who live, work and create in our region. St. Louis on the Air host Don Marsh and producers Mary Edwards, Alex Heuer and Kelly Moffitt give you the information you need to make informed decisions and stay in touch with our diverse and vibrant St. Louis region.