The town of Alba Pompeia was limited by the defensive walls. Their circuit enclosed all the eight
sides of the city. The walls were characterized by the presence of the gates, in correspondence with
the main streets of the city, by some towers and by an interesting structure identified with a barrackwarehouse.
The town was laid out with streets in a grid pattern: the intersection between the main north – south
oriented road (the cardus maximus) and the east – west one (the decumanus maximus) was the
model of a network of orthogonal streets. The urban plan based on 52 squared quartiers (insulae).
The streets were 5,5 meters wide and flanked by dirt sidewalks. Their surface consisted of river cut
cobblestones rammed in the soil, limited by vertical rammed stones along the edges. The centres of
the crossroads were occupied by manholes that ran the waters in the sewers.
The town had three main entrances that corresponded to the main three gates situated at the
southern bottom of the cardus maximus and the east and west bottoms of the decumanus maximus.
The northern one had only a secondary gate because of the small space that separated the city-walls
from the river Tanaro.
1) Groma from Libarna (Ligurian Archaeology Museum, Genova-Pegli). The groma was a
survey instrument. It was used to survey straight lines and right angles, thence squares or
2) Roman crossroad preserved in the Palazzo Calissano archaeological site, in Alba
3) Reconstruction of the crossroad with the surfaces, the arcades and the façades. In the
foreground, a photo of a part of the sewer crossroad