The Lascaux grotto consists of a main cavern 66 feet wide and 16 feet high. The walls of the cavern are decorated with some 600 painted and drawn animals and symbols and nearly 1,500 engravings. The pictures depict in excellent detail numerous types of animals, including horses, red deer, stags, bovines, felines, and what appear to be mythical creatures. There is only one human figure depicted in the cave: a bird-headed man with an erect phallus. Archaeologists believe that the cave was used over a long period of time as a center for hunting and religious rites. The cave contains nearly 2,000 figures, which can be grouped into three main categories: animals, human figures, and abstract signs. The paintings contain no images of the surrounding landscape or the vegetation of the time. Most of the major images have been painted onto the walls using mineral pigments, although some designs have also been incised into the stone. Many images are too faint to discern, and others have deteriorated entirely. Over 900 can be identified as animals, and 605 of these have been precisely identified. Out of these images, there are 364 paintings of equines as well as 90 paintings of stags. Also represented are cattle and bison, each representing 4 to 5% of the images. A smattering of other images include seven felines, a bird, a bear, a rhinoceros, and a human. There are no images of reindeer, even though that was the principal source of food for the artists. Geometric images have also been found on the walls. The most famous section of the cave is The Great Hall of the Bulls where bulls, equines, and stags are depicted. The four black bulls, or aurochs, are the dominant figures among the 36 animals represented here. One of the bulls is 5.2 metres (17 ft) long, the largest animal discovered so far in cave art. Additionally, the bulls appear to be in motion. A painting referred to as "The Crossed Bison", found in the chamber called the Nave, is often submitted as an example of the skill of the Paleolithic cave painters. The crossed hind legs create the illusion that one bison is closer to us than the other. This visual depth in the scene demonstrates a primitive form of perspective which was particularly advanced for the time.