Important news: Big parts of Line A of Rome's metro system will be closed in August. And, yes, Rome's metro system has only two lines. So take note!
For work and for construction of Rome's third metro line, Linea C, Metro A has already been closing at 9pm. Here are the new changes for August:
From July 30-August 3, there won't be any service on Line A between Termini and Anagnina. Instead, there will be replacement bus services. (This half of the metro line includes stops at Vittorio Emanuele, Manzoni, and San Giovanni). Until 1:30am, though, there will be service in the other direction, from Termini to Battistini (if you're traveling to Rome, you're more likely to use this side of the line, which includes stops at Barberini, Spagna, and Ottaviano-San Pietro).
From August 4-29, there won't be any service between Termini and Arco di Travertino, a section of the line that includes Vittorio Emanuele, Manzoni and San Giovanni, although that part will operate on Aug. 6, 13, 20 and 27. (They're all Saturdays). Until 9pm every day, the metro will be active in the other direction, from Termini to Battistini, as well as from Arco di Travertino to the end of the line at Anagnina. And on those Saturdays, Aug. 6, 13, 20 and 27, the line will be active between Battistini-Termini and Arco di Travertino-Anagnina until 1:30am.
Don't worry, though — the metro doesn't connect lots of major tourist sites in Rome (there's no, say, Pantheon or Piazza Venezia stop… something they're more or less trying to change with Line C), and in the summer, it can be uncomfortably hot and crowded. So here are six alternative modes of transport for those hot Rome days.