Pensacola Dam and Grand Lake O' the Cherokees provide flood control for the Grand River and produce hydroelectric power for Grand River Dam Authority. It is the world's longest multiple arch dam, spanning approximately one mile. The dam towers as much as 150 feet above the riverbed. The lake is 43,500 acres and has about 1,300 miles of shoreline, more than any other lake in the state. Grand Lake O' the Cherokees is one of the most popular tourist attractions in Oklahoma. Tours of the historic dam are held regularly between Memorial Day and Labor Day. Some of the best rock crawling in the country for four wheelers is located at the south end of Grand Lake (directly below the dam) between the towns of Langley and Disney. The area has been nationally recognized as a destination for 4x4 users.