What Roman theatre in Rome was built in the late 1st century BCE and named after Augustus's nephew?

The Roman theatre built in the late 1st century BCE and named after Augustus’s nephew was the Theatre of Marcellus.

Julius Caesar cleared the site, but construction advanced under Augustus. The theatre was sufficiently complete for part of the ludi saeculares celebrations in 17 BC, was completed in 13 BC, and was formally inaugurated in 12 BC. Augustus named it for his nephew Marcus Claudius Marcellus, who had died in 23 BC.

The building stood in Rome’s Campus Martius and could hold roughly 11,000 to 20,000 spectators. Its semicircular cavea, arcaded exterior, and ordered columns became influential models for later Roman theatres. It was built mainly from tuff, concrete, and travertine, with fired Roman brick also used.

The theatre later lost its original function and was partly converted into a fortified residence and then a palazzo. It is often confused with the earlier Theatre of Pompey, another major performance venue in Rome, but the Marcellus theatre belongs to the Augustan age.