Largest building in Kentucky lies underground

A 40-year mining site now welcomes visitors to zipline, bike and even drive the 17 miles of roads below the city at Louisville Mega Cavern.

After its mining operation closed, private investors converted the space focusing on the environment and security. Since 1990, they have offloaded recycled concrete, brick, block, rock and dirt to the 4-million-square-foot site for fill and construction.

With wet summers and dry winters, the cavern remains 58 degrees year round, the same average temperature of the area for thousands of years.

Today, it is classified as the largest building in the state, above or below ground.

– Rebecca Hastings, The Kentucky 100