Wadi Al-Hitan

Wadi Al Hitan, Arabic for Valley of the Whales, lies in Egypt's Faiyum Governorate about 150 kilometers southwest of Cairo. Its rock dates to the Middle and Late Eocene, some 40 to 41 million years ago, laid down in three marine units, the open marine mudstones of the Gehannam Formation, the yellowish sandstones of the Birket Qarun Formation that hold most of its whale fossils, and the lagoonal mudstones and limestones of the Qasr el Sagha Formation, together preserving some 1,500 marine vertebrate fossil skeletons including archaeoceti, early whales whose small hind limbs document the transition from land to sea.