Miles of man-made caves and tunnels are currently used for cultivating mushrooms.

The great Italian Renaissance painter was laid to rest here in the Chapel of Saint-Hubert.

This museum preserves over-the-top masterpieces that once qualified artisans for membership into a medieval guild.

Limestone grottoes turns everyday objects into stone.

In a pedestrian tunnel on North Carolina State’s campus resides an expressive and artistic free-for-all.

This former train tunnel is filled with lines from a poem crafted by Robert Louis Stevenson.

This colorful creation wasn't always a welcome part of Toronto's Moccasin Trail Park.

Discovered by cows, these upstate New York show caves are presented with a healthy dose of psychedelic folk art.