Huellas de Acahualinca
The fossilized footprints of Huellas de Acahualinca were discovered in the late 1800s, and a museum was built on the site in the 1950s to protect it. Scientists have differed over the years about exactly how old the footprints are, with findings ranging from 2,000 to 6,000 years old, but in any case they’re a powerful reminder of the human history in the area. The museum is open Monday-Sunday, and there’s a small admission charge. Also note that the museum isn’t in the city center, so it’s a short taxi ride to get there.