Talk about recycling. In Wisconsin, the state government has converted abandoned railroad lines into paved, bike-only paths. The state is home to a number of these so-called rails-to-trails pathways, but the best may well be the Elroy–Sparta trail. It winds for 32 miles through some of the more rural parts of Wisconsin. What's even cooler, it passes through three old stone train tunnels, varying in distance from 1/4-mile to 3/4-mile. Coolest of all: no hills. The trail is almost entirely flat.
Daily trail pass: $4.