An on-site museum housing and featuring the millions of fossils excavated in the nearby tar pits (which are inaccurately named, as was repeatedly explained to us).
All around excellent. There are Imax shows, live saber tooth puppet show, a mummified baby mammoth, lots of huge fossils, a place where you can test the stickiness of tar for yourself, and more and more.
Besides all that, it's an active excavation and conservation site, so you get to watch and talk to people cleaning the actual fossils, both inside in a lab and outside on location.
Children were loving it, and us adults too honestly.