Planetarium
Built in 2010 to commemorate the 400th anniversary of Galileo's astronomical discoveries, the modern planetarium doesn't seem to fit in with the rest of Plaza Vieja's colonial grandeur; nonetheless, it makes for an interesting visit. Inside there's a scale model of the solar system, as well as a range of interactive games and a large viewing theater, which currently only has audio descriptions available in Spanish.
Reservations must be made in advance.