Waipiʻo Valley is a valley located in the Hamakua District of the Big Island of Hawaiʻi. "Waipiʻo" means "curved water" in the Hawaiian language. It was the capital and permanent residence of many early Hawaiian aliʻi (kings). The valley floor at sea level is almost 2,000 ft (610 m) below the surrounding terrain. A steep road leads down into the valley from a lookout point located on the top of the southern wall of the valley. The road gains 800 vertical feet (243.84 m) in 0.6 miles (0.9 km) at a 25% average grade, with steeper grades in sections. This is a paved public road but it is open only to 4 wheel drive vehicles. It is the steepest road of its length in the United States and possibly the world. The valley floor below the cliff is littered with crumpled cars that lost conrtol on the road. The shore line in the valley is a black sand beach, popular with surfers. A few taro farms are located in the valley. Several large waterfalls fall into the valley to feed the river which flows from the foot of the largest falls at the back of the valley out to the ocean.