Someone is about to open a 320,000 sq ft indoor, 100 feet underground bike park in/near Louisville.
Louisville Mega Cavern
It's in an abandoned limestone mine.
Raining? Ride in comfort, it's underground.
Cold out? Ride in comfort, it's 58 degrees, all the time.
Too hot out? Ride in comfort, it's 58 degrees, all the time.
45+ trails, jumps, dual slalom, BMX, single-track, and a cross country course.
Link