Ostia Antica was a pleasant surprise. Having just visited Pompeii, the pinnacle of Roman preservation, I half expected Ostia Antica to be nothing more than broken blocks and mounds of earth. The city, however, is remarkably intact - oh there was no over-baked bread left in the ovens like in Pompeii, but this micro-preservation of Pompeii has largely been removed to the museum in Naples anyway, and the macro-preservation of Ostia Antica was as stunning as Pompeii.
Ostica Antica was probably the first colony of ancient Rome, a natural first step to empire as it was situated at the mouth of the River Tiber, making it the perfect site for Rome's seaport. After thriving for maybe 1000 years, Ostia fell into decay with the end of the Roman Empire, with silting of the Tiber taking away its capacity to act as a port and the death of the Roman trading network. Despite a far slower death than Pompeii, the city is well preserved, especially the magnificent series of mosaics of the Baths of Nepture and around the Square of the Guilds.