Tens of thousands of years ago, dire wolves hunted ground sloths and camels while herds of gigantic mammoths lumbered past cypress trees. All of this happened where Los Angeles now stands, and many of these animals are still well preserved in the bubbling black goo below.
Since 1913, scientists have been pulling bones and other fossils out of the La Brea tar pits. In fact, some of the best evidence for these species comes from the pits, which are just steps from an art museum and office supply store.
Despite the name, the thick liquid in the pits isn't tar. It's asphalt. "It's this crude oil that's just coming up and has been up for the last thousand years," Matt Davis, a paleontologist at the Natural History Museum of Los Angeles County, told Business Insider.
The tar pits have preserved everything from massive mammoths to specks of pollen. "That's really rare for a fossil site," Davis said. It's unusual that both plants and animals fossilize in the same place, he said.
At La Brea, "you get a whole ecosystem," he said, "and that lets us really reconstruct what the Ice Age looked like."
During a recent visit, Business Insider visited the pits and spoke with La Brea's scientists who showed us how fossils of mammoths, dire wolves, and other species go from covered in gunk to ready for display.