The La Brea Tar Pits is known for having the largest and most diverse collection of extinct plants and animals from 10,000 to 40,00 years ago.
If you remember or saw the movie Volcano with Tommy Lee Jones, the volcano erupted near the La Brea Tar Pits which is located in the Wilshire district of Los Angeles.
There is a paleontologist lab inside of the museum where you can actually watch some of the paleongologist cleaning the fossils. They are still excavating fossils.
The pond in front of the museum, which is the tar pit, contains life size replicas of some extinct animals. It still smells of tar that trapped these animals and you can see bubbles forming on the surface. The tar preserved these bones/fossils in pristene condition.
Imagine this tar pit in the heart of Los Angeles. Stand facing the tar pit and imagine none of the buildings and none of the traffic around you - just wide open land with extinct animals roaming free. Imagine them coming to this watering hole and finding it a trap from which they can't escape. Their bones are still being excavated in the heart of this city for us to view and study.