Here's a cool new initiative: The Colosseum will be illuminated and kept open for nighttime guided tours in late June, July, and September. (In typical Roman fashion, there will be a break in August.) You'll see a special exhibition on the Flavian Dynasty and 2,000-year-old Emperor Vespasian, who oversaw the Colosseum's construction.
English-language tours will be available at 9:30 and 10:30 p.m. for €15/$21, according to the Italian cultural site piericci.it. Call 011-39/06-3996-7700 to make a (required) reservation.
The AP also reports that new daytime tours will cover the Temple of Romulus, previously closed to the public, and two residences on the Palatine Hill: the House of the Griffins, which dates to the 2nd century B.C., and the House of Livia, known for its frescoes.