Here, 20 miles northwest of Ann Arbor, you'll find three trails: the 17-mile Potawatomi Trail, the 5.1-mile Crooked Lake Trail and the 1.9-mile Silver Lake Trail. The routes are shared with hikers. If you double the length of Pontiac Lake and replace the rocks with roots, you have Poto. Trails from 1.9 to 17.5 miles round trip. Biking season: All year (8 a.m. to 10 p.m.). Other activities include bicycling, boating, camping (reservation), canoeing, fishing, hiking, horseback riding, picnicking, swimming, water skiing, cross-country skiing, snowmobiling. Dining in Chelsea, Dexter, Pinckney. Bike shops in Chelsea (Chelsea Bike & Sports-313/475-9371), Pinckney (Village Cyclery-313/878-0117) Bike rentals: Pinckney (Village Cyclery).