Porticus of Octavia

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The Portico of Octavia, Rome
Entrance to the Porticus of Octavia
The Porticus Octaviae (Porticus of Octavia) was originally built by Quintus Caecilius Metellus with the proceeds of his victory in Macedonia in 146 BCE. It enclosed two victory-temples, which were dedicated to Juno Regina and Jupiter Stator. The quadriporticus, which measured 119 metres by 132 metres, and comprised in the region of 300 columns, was rebuilt by the emperor Augustus (r. 27 BCE - 14 CE) in about 25 BCE and dedicated to his sister Octavia. It later incorporated a library in memory of Marcellus, Octavia's son, who died in 23 BCE. 

The porticus was later restored by the emperor Septimius Severus (r. 193-211) following the outbreak of a fire, as detailed in the inscription. 
Reconstruction of the Portico of Octavia, Rome
Reconstruction of the Porticus of Octavia