Previously, abandoned limestone mines were only good for one thing: low-budget horror movies. But some resourceful types in Louisville, Kentucky, have come up with an even better idea: build the largest indoor bike park in the world.

The Louisville Mega Cavern has opened the Mega Underground Bike Park, and with a whopping 17 miles of space to play in, we’re officially calling this a better day than the Kentucky Derby. Besides having the world’s only underground off-road bike course, there’s also zip lines, a ropes course, and plenty of event space. And don’t forget, being 100 feet underground means perfect weather 24/7. Spread out over the 320,000 square feet are 45 trails, jump lines, pump tracks, slalom courses and more. It just opened to the public, and bike rentals begin in April at $24 per person for half a day.

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