Darwin Island (also known as Culpepper Island, after the famous naturalist and English Lord Culpepper) was named after Charles Darwin. Its exceptional underwater life is an important reason that Galapagos is considered one of the Seven Underwater Wonders of the World. It is the northern-most island, located some 160 km NW of Isabela on the Wolf-Darwin volcanic ridge. Darwin and Wolf Islands are the most remote in the archipelago, with Darwin about 21 km to the north of Wolf. Large schools of Hammerhead Sharks frequent the waters around Darwin Island. The first terrestrial visit to Darwin Island took place in 1964 with the aid of a helicopter. Darwin, like Wolf Island, is the tip of a massive, mostly subsurface volcano that rises over 1,000 m above the sea floor. Now extinct, it is estimated to be from 400,000 to 1.6 million years old.