The Rajiv Gandhi Regional Museum of Natural History is one of four regional natural history museums in India, opened in Sawai Madhopur specifically because of the town's proximity to Ranthambore. The collection covers the natural history of the Thar Desert and the Aravalli ecosystem: dioramas of wildlife in their habitats, geological specimens from the region, botanical specimens, and a specific focus on the ecology of dry deciduous forests.
It is worth a visit either before your first safari (to get a sense of what you might encounter in the forest) or after (to identify what you actually saw). The museum is a government facility with no entrance charges, and it is rarely busy. Allow an hour to get through the galleries properly.