Ostia Antica is a large archeological site, close to the modern suburb of Ostia, that is the location of the harbour city of ancient Rome, 15 miles southwest of Rome. "Ostia" is a derivation of "os", the Latin word for "mouth". At the mouth of the River Tiber, Ostia was Rome's seaport, but due to silting the site now lies 3 kilometres from the sea. The site is noted for the excellent preservation of its ancient buildings, magnificent frescoes and impressive mosaics.