The best thing FREE about Rome is exploring the city itself. There can be a surprise around every corner: a giant marble foot (maybe not a surprise when you realize are on Marble Foot Street), a beautiful fountain, a magnificent church, or an ancient arch. So, put on some comfortable shoes, grab a map, and start wandering.
Forum of Caesar (Foro di Cesare), built between century BC and century AD, with the colums of the Temple of Venus Genetrix in front and the Monument to Vittorio Emanuele II in the background, at night. Rome, Province of Rome, Italy.