This was one of the richest monuments in Rome. The original portico was built in the 2C BC by Cecilius Metellus, conqueror of the Macedonians. It was then rebuilt by Augustus, who dedicated it to his sister Octavia and included two public libraries inside the building, as well as an assembly hall where the Senate occasionally met. The portico was later further modified by Septimus Severus (193-211).