This is where it all began, some 20 years ago, with a few guys riding very heavy bikes up and down the steep, winding single-track trails of Mount Tam. It's easy to see why the sport has its origins here: You'll find more than 50 miles of trails that cross through redwood and madron forests and open out upon immaculate ocean views.

And Mount Tam is only one feature of the larger landscape of Marin County, which harbors enticing trails everywhere you look. This may be the perfect mountain-biking playground; countless rides are possible. The 22-mile Mount Tam loop is one of the favorites: You'll find plenty of steep single-track, a few arduous ascents, great views, and to quench your accumulated thirst, an English pub at the end. If you're feeling a little less ambitious, try the ten-mile Bay View–Shoreline trail, a smooth single-track that winds through forests of wild oak.