What do BMX, skateboarding, and street hockey have in common?
They're all sports that worked their way from the underground to the mainstream. The X-Games became a showcase for alternative sports that have their roots in backyards and abandoned lots, but there are constantly new sports evolving.
If there's a way to make something faster, harder, or more dangerous, people will find a way to do it...and then they'll turn it into a competition.
There are several sports in the world that have been emerging on the underground scene for a while now, and it's about time they got their due.
Here are 20 awesome underground sports.