You have heard stories and legends... but are they true or mere tales? What am I talking about? Why, the underground tunnels spanning the entire state of Colorado, of course! Around the time of Colorado's conception, tunnels under the streets of bustling downtown areas were a common addition, serving as below-ground entrances and storage areas for local businesses. Sadly, these fascinating structures are now on the Colorado Endangered Places List. Let's take a look:

From Trinidad to Denver and Grand Junction to Fort Collins, Colorado is home to a series of subterranean tunnels primarily located beneath the front area of commercial buildings, with some branching out into side or back alleys.

The non-profit organization Colorado Preservation, Inc. works to protect locations with historical significance that are in danger of being destroyed, and the subterranean tunnels were added to their list of most endangered places in 2018.

So what, exactly, was this underground network used for?

During the 19th century, there were no paved roads. The streets were quite muddy and, as horses and carriages were the main forms of transportation, things could get a little... stinky... after the horses passed through. In general, it wasn't a pleasant place to walk around.

The solution: create an underground area for those on foot to avoid the messy streets.

The tunnels led between many of the main buildings in town and some were actual subterranean storefronts. It was like a whole underground city!

Other tunnels were used as storage spaces.

It was a practical way to increase the square footage of a structure beyond the basement space.

Many entrances to the tunnels are found on the first floors or in the basements of historical buildings; however, some are accessible via street level stairwells.

If you've ever stood on a sidewalk with small glass circles set into it, you likely thought it was just a decorative feature, but these actually acted as little skylights to bring natural light to an underground space.

Though incredibly useful in their heyday, the underground tunnels also presented a few unique challenges and dangers.

When the Arkansas River flooded in 1921, it drowned the tunnel system beneath Pueblo and carried in silt that could not be dug out, so many of the damaged areas were simply walled off.

Due to their seeming lack of practicality in the modern era, the remaining historic treasures are in danger of being filled in, which has already taken place in several locations.

By bringing awareness to these unique and endangered tunnels, Colorado Preservation, Inc. hopes to save this special part of Colorado history.

To get a better look at Colorado's Downtown Underground, check out this video from Colorado's Most Endangered Places:

For more information about the underground tunnels, other historic preservation sites around the state, and ways to get involved in the projects, visit the Colorado Preservation, Inc. website here.

Did you know about these unique hidden locations beneath our streets? Are there other secret spots that you know of? Let us know in the comments below!

To learn even more about what lies under the streets of Denver, click What’s Hidden Underground In This Landmark In Denver Is Unexpected But Awesome.