My buddy sent me this link to Adventure Journal with an article about indoor MTB parks. I'm not the biggest fan of being indoors, really. That's why I've killed two gym memberships in the last two years. It's not the exercise that's hard... it's the four walls around me that make me claustrophobic. But I have to admit, these parks seem pretty cool.
Head on over to the article and check it out. I could see these things drawing a crowd.
Get out there (contradictory to this post, I know).