The world's oldest public museums, founded in 1471 when Pope Sixtus IV donated a collection of bronzes to the people of Rome. The two palazzi flanking Michelangelo's Piazza del Campidoglio hold an outstanding collection of classical sculpture: the equestrian bronze of Marcus Aurelius (the original; a copy stands in the piazza), the Capitoline Wolf, the Dying Gaul, and the Capitoline Venus. The rooftop café has one of the best views over the Roman Forum.
The piazza itself, designed by Michelangelo though completed a century after his death, is worth lingering in. Allow 2 hours for the museums.