Vercelli, Vercellae for the Latins, is one of the oldest urban site in the north of Italy. It has been the first town in Piedmont to have the physical and political structure of the "città-stato", one of the first example of structured urbanisation in the V century BC. In that period, Vercelli, oppidum of the Celts settled in this area, had an administrative organisation and a district wider than the actual one, based on the model of the Greek colonies of the south of France, with which it had relationships. The contact with Rome and its civilisation brought an evolution in this town: firstly it was a mere centre of commerce situated in a strategic area, then it rapidly assumed costumes and magistrates from Rome, even if it was simply a group of villages developed around an administrative and military centre. The first written documents about its history are dated 43 BC: a letter from Bruto to Cicerone and a stele in which is mentioned, both in Latin and in leponzio, a magistrate of the "città-stato". With August, Vercelli became a roman municipium: it assumed the characteristics of the roman town. New houses, temples, markets, theatres, amphitheatres, a new fluvial harbour, aqueduct and the massive walls with a wide ditch were built. Its inhabitants, in the first century AD were about 20.000.The roman walls are the first example of walls in this town, even if an older and smaller perimeter probably surrounded the original oppidum. Recently, a part of the roman walls has been discovered in via Q. Sella. The first perimeter of walls was refurbished in the Tardoantico: towers and fortifications were added. Then they were demolished. The complete perimeter hasn't been discovered yet, but it had to be not much smaller than the perimeter of the medieval walls. In the Middle Age, the towns in the north of Italy were very probably smaller than in roman period, because during the longobardo reign the urban centres occupied a small part of the old roman centres. Around 1100, Vercelli was a medieval commune and it needed a new and wider perimeter of walls, wider than old roman centre. The roman walls in fact were only few tens of metres away from the more external medieval walls. Between 1300 and 1500 the Visconti and the Savoia families transformed the town in a stronghold with a new castle, a citadel and new walls. Therefore they occupied the same perimeter of the medieval walls, superimposing to them in some parts. These massive bastions (ramparts), visible in the engraving of the Theatrum Sabaudiae, were afterwards demolished after the French conquest in 1704 and the bricks were recovered to build new houses. The walls were replaced by the allee, avenues that still today surround the centre of the town.These successive modifications of the urban walls, produced transformations of the centre of the town from the V century BC on. In this narrow space, history has left on the front of the houses traces visible still today. In the subsoil, the ruins of the town stratify from the roman period on; the medieval structure is formed by houses with towers and forts build by the noble families. The centre of the town keeps a great architectonic and archaeological value and it would deserve careful studies by the town council (municipality) in order to exploit its great potentiality.