It’s rare that you find an inviting BRB (Big Red Button) just sitting out in the world, with no warning signs, and no indication as to its purpose. Yet hidden in a shallow niche on Houston’s Preston Street Bridge is just such an enigma. Go ahead and press it.

The button is part of an ecological art installation that helps keep the bayou below the bridge from becoming a bog of eternal stench by, well… making it look like the Bog of Eternal Stench. Any passerby on the bridge is free to press the button and when they do so, the waters below will begin to bubble and churn as though they have accidentally raised some unholy bog creature. In fact they have just made the bayou a bit less evil.

In order to keep the waters of the bayou from becoming vile and stagnant, they need to be stirred up and oxygenated. To this end, the Big Bubble was created in 1998 by artist Dean Ruck as both an intentionally mysterious bit of public art, and as an environmentally helpful bit of infrastructure. When the button is pushed, a blast of oxygen is released underwater, creating a roiling bubble just off the side of the bridge. It keeps the water from becoming still and flat, as well as being pretty entertaining.

Of course not everyone is bold enough to go around pushing mystery buttons, so the Big Bubble is triggered automatically throughout the day. Passersby who wantonly press the button are simply keeping the bayou even more healthy.

Update April 2019: It is currently not accessible.