Ostia Antica is an ancient Roman city and the port of Rome located at the mouth of the Tiber. It is near modern Ostia, 25 km southwest of Rome. Due to silting and the invasion of sand, the site now lies 3 km from the sea. The name Ostia derives from Latin os 'mouth'. Ostia is now a large archaeological site noted for the excellent preservation of its ancient buildings, magnificent frescoes and impressive mosaics.