Photos of the La Brea Tar Pits. The La Brea Tar Pits are located in Hancock Park and represent one of the world's richest collection of fossils from the Pleistocene era. The tar pits were created by asphalt that seeped up from beneath the ground to form black sticky pools that would trap animals such as mammoths, wolves, sloths, and saber-toothed cats. Over time, the asphalt would fossilize and preserve the bones of the unfortunate animals. Today, the La Brea Tar Pits still contains active dig sites and during the summer visitors can watch the excavation of Pit 91.