Isabela is the largest island in the archipelago. At over 4500 square kilometres it accounts for over half the Galápagos total land area. Inland much of the terrain is rough and impassable. The island has six volcanoes, several of which are still active. Wolf, the tallest volcano, reaches 1700 metres. Landing points are usually on the western side of the island. Marine life is particularly good on Isabela with Common Dolphins, Galápagos Penguins and whales.