Rome took the control of the nearby gold-bearing exploitations and of their transport into the metropolis, which explains this first military settlement and the following decision to establish the capital of the Roman administrative demarcation in Asturica, from the Cantabrian Sea to the west of the valley of the River Duero.

The fortification we can see consists of two moats in V-shape section, parallel and exterior, of the kind of fossae fastigatae. They were dug in the natural gravel of the edge of the hill in which the city is settled to increase their defensive effectiveness.

Around the first third of the first century A.C, the interior moat was rendered useless and the construction of a stone wall began, which would protect the city. This first wall had circular towers, one of which was laid in the moat, also invaded by the first buildings of the city , the street and sanitary networks. Later on, in the Flavian age, this first fortification was abandoned and the city extended its area comprised by another stone defence, of older history.