The sheer number and variety of wildlife both on land and in the water of the Galápagos is quite remarkable. Because of the islands’ isolation and remoteness, many of these species are found only in the Galápagos and have not changed much since prehistoric times. The Galápagos’ famous marine iguanas, albatross and giant tortoises continue to amaze scientists and delight tourists. Many unique species occur in great concentrations. For example, marine iguanas bask on the beaches by the hundreds, and on certain islands hundreds of birds may be seen at one time.