The archaeological work around Portus tells us more about how the Romans lived and how important the port was. The Roman empire marched on its stomach and even after the huge artificial harbour of Portus was built when the volume of freight had become too much for the original harbour at Ostia ships would still have had to queue to get to the wharves and unload. They carried basic foodstuffs such as grain, wine, oil and olives, the ubiquitous sauce made of rotted fish which was the ketchup of its day, and luxuries including exotic fruits and spices. Although thousands of workers would have lived in the port, they might well have seen noble visitors pass by. Emperors kept a close eye on Portus, staying in a palace by the water: if the grain supply failed, there would be riots in Rome. Luxuries coveted by Rome's increasingly wealthy citizens streamed through the port. Shipwrecks have revealed the scale of the trade: marble to face new imperial buildings, lead and bronze ingots, unguents and fragrances, silks and dyes, Baltic amber, linen and cotton from Egypt and India, gold, silver and gems, marble and bronze statues stripped from temples in Greece. Other ships bore living cargo: exotic animals from Africa and India and slaves, all destined for rich households or to provide one bloody afternoon's entertainment in the amphitheatre.