..It's a National Park - nah - we'd never heard of it either!! We're staying just outside of Montrose, CO. Very nice. Rode the 15 miles to the park. Did a small hike around the rim area. It's 2000ft deep and no more than 9m wide - much less in places. It's 'black' because it is so dark and dingy and inaccessible it was this great big 'black hole'. Eroded away by a storming debris-laden Gunnison river on a misson - it drops an average of 96 feet per mile - up to 480 feet in a particular 2 mile stretch!!