Waipio Valley Road is the steepest paved public road in the world.

Waipiʻo Valley is a valley located in the Hamakua District of the Big Island of Hawaiʻi. "Waipiʻo" means "curved water" in the Hawaiian language.
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 rises 800 feet (240 m) in 0.6 miles (1.0 km) at a 25% average grade, with significantly steeper grades in sections. Some portions of the road can reach up to a 45% grade,which would make Waipio Valley Road the steepest in the world, compared to Baldwin Street's 35%. 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. 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.