I've been wanting to visit the La Brea Tar Pits in Los Angeles for some time now, and finally was able to do just that! The La Brea Tar Pits are part of the Natural History Museums of Los Angeles County, which provide an overview of the pits:
Right in the heart of L.A. sits the world's most powerful gateway to the Ice Age. The asphalt seeps at La Brea Tar Pits are the only active urban fossil dig site in the world. Plants and animals from the last 50,000 years are discovered here every day. Outside, you can watch excavators carve fossils out of the asphalt. Inside the museum at La Brea Tar Pits (established in 1977 as the George C. Page Museum), our staff prepares these discoveries in the see-through Fossil Lab. You'll see the final result in our exhibitions: extraordinary saber-toothed cats, mammoths, dire wolves, and mastodons, as well as the tiny, but scientifically significant, microfossils of insects, plants, mammals, and reptiles. The Tar Pits help us understand life around Wilshire Boulevard long before we got here, and what lies ahead as climate and habitats continue to change.
The main attraction of the outdoor pits is the mammoth family. Los Angeles Times explains that
The first fiberglass mammoth was driven to the tar pits in 1967 on a trailer pulled by sculptor Howard Ball's 1958 Volkswagen. Its baby and female companion soon followed.
The outdoor signage at the pits includes an image of that first mammoth making its way down Wilshire Boulevard. What a sight that must have been!
You can visit the outdoor section—where the tar pits are—for free, but to see the fossils and exhibits, you'll need to pay to get into the museum. I found it all fascinating, so I recommend doing both. If you don't have the cash or the time to see the museum, a visit to the outdoor (free) pits is still worth the trek.