An 800-acre national park in a rocky, dramatic landscape where the Potomac River plunges some 76 feet through narrow Mather Gorge. Ranger-led talks and nature walks. Fifteen miles of trails. Picnic areas. Daily 7 a.m.-dark, visitors center 10 a.m.-4 p.m. $3 per individual, $5 per car (good for three consecutive days).