Not all biking is mountain biking. Even if you have a mountain bike.
The Sparta-Elroy trail is part of an old railroad bed, for the Chicago-Northwestern Railroad. Its a flat crushed granite trail. It draws hundreds of tourists a week, and one of the biggest draws on the trail is the set of railroad tunnels that you have to walk through. The tunnels are all ~60 degrees (nice on a hot day) and the longest one is almost 3/4 mile.
Location:
Sparta, Wisconsin
Directions:
You can pick up the start of the trail out in front of Speed's Bike Shop, 1126 John Street, Sparta, Wisconsin 54656