Cosa's arx on Via Sacra was the city's place of worship. It looks out onto the sea and Orbetello in a very evocative location.
The arx is divided into two buildings. The biggest is thought to have been the Capitolium, which was used for ceremonies tied to the foundation of the city. The temple would have had thick columns and bright terracotta tiles in a style that was typical of the Etruscan-Italic era.
Archaeologists don't think the building is any older than 150 BC. It's likely an older temple dedicated to Jupiter stood in its place earlier.
The smaller building is another temple thought to have been dedicated to the Roman god of fertility and the sea Mater Matuta.