How big are the pits? From the pics they look relatively small, like a neighborhood pond.

According to google maps satellite imaging the main tar pit is about 322 ft long and 120 ft wide. The smaller ones range from about 25 ft to 50 ft in diameter

Not very wide, though there are multiple pits. At some of the pits they are still finding new artefacts. The biggest one has a fence around it. Looks more like a mini lake.

They are quite small and the museum is very small as well.

Pit is not an accurate description. The large one you see in the front is a man-made excavation pit. The others are more puddle sized.