When winter arrives in much of the world, cyclists such as BMXers and freestyle mountain bikers are limited to riding in warehouse-style indoor bike parks. These places can be fun, but they're still ... you know, in a building. Such is not the case, however, with the just-opened Mega Underground Bike Park. Claimed to be the largest indoor bike park in the world, it's situated 10 stories (100 ft/30.5 m) underground in a disused limestone mining cavern.

Located in Louisville, Kentucky, the bike park measures 320,000 sq ft (29,729 sq m) and features over 45 looping dirt trails. These include jump lines, pump tracks, dual slalom, BMX, and easier-to-ride single track. The temperature stays at a comfortable 60ºF (15ºC), year-round.

The facility just opened on Feb. 9, and so far users have to supply their own bikes. As of sometime in April, though, rentals should be available.

Admission prices appear to be fairly reasonable, starting with US$24 getting you four hours of use, or $40 getting you eight.

You can see the bike park in use, in a video posted on YouTube. It's actually just one part of the Louisville Mega Cavern, which also features a zip line, ropes course, tram tours and other attractions.

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