British archaeologists have unearthed a Roman amphitheatre overlooked by previous excavations at a site to the north of the Tiber that once served as the maritime gateway to imperial Rome. During their three-year dig close to Rome's Fiumicino airport, the researchers also found a shipping canal, luxuriously decorated rooms and a colonnaded garden, suggesting the port was a regular way station for Roman emperors. Portus, ancient Rome's Mediterranean harbour, now lies two miles inland because of sedimentation. But it was once a basin a little over a mile wide serving 350-tonne vessels unloading grain, silk and wild animals. The 1m dig, led by the University of Southampton, assisted by Cambridge University and the British School at Rome, focused on the remains of a palace built between the port's main basin and a hexagonal inner harbour where goods were unloaded into 300-metre-long warehouses supported by 15-metre brick arches before being transferred by canal to the Tiber for transport to Rome. While researchers had uncovered warehouses previously, the presence of a theatre was only hinted at by the archaeologist Rodolfo Lanciani during an 1860 excavation, the last big dig at the site. This time, the British team, aided by the archaeology superintendent of Ostia, brought in magnetic sensors, ground radar and metal probes. "The current passes between the probes and we can see the resistance from buried remains," said Graeme Earl, one of the team leaders. The careful search disclosed the curved walls of the amphitheatre, dated by the project's director, Professor Simon Keay, to the 3rd century AD. "Its design, using luxurious materials and substantial colonnades, suggests it was used by a high-status official, possibly even the emperor himself it could have been games or gladiatorial combat, wild beast baiting or the staging of mock sea battles. But we really do not know." The ground scans revealed a garden, cisterns, a 250-metre by 60-metre room attached to the palace and a 90-metre-wide canal linked to nearby Ostia. Keay also found a head using the more low-tech method of almost tripping over it. "The bulldozer was clearing topsoil and I saw to my horror a human face looking at me. It is one of the most spectacular finds to date," he said. The exquisite sculpture, which could depict Ulysses, "was the property of someone with a lot of culture and disposable income", said Keay. The luxury fittings extend to fine blue and white marble in a lavatory. "There was probably running water beneath the marble toilets to prevent smells," said Rose Ferraby, an archaeologist. Holes in the front panel of the loo seat let users clean themselves with a brush, she added. Built by Claudius in AD46, Portus was expanded by Trajan in the second century. The importance of grain shipments getting through to Rome became clear in AD62 when a storm sank 200 ships in the main harbour, prompting bread shortages and riots. "By that time Rome had long outgrown Italy's ability to feed it and the city owed its existence to the port," said Keay. "That makes Portus one of the most important archaeological sites in the world."