Roman theater started by Julius Caesar & pre-dating the Colosseum, the setting for summer concerts. Builder Julius Caesar Augustus Caesar / Marcus Marcellus, Founded 13 BC. The Theatre of Marcellus (Latin: Theatrum Marcelli, Italian: Teatro di Marcello) is an ancient open-air theatre in Rome, Italy, built in the closing years of the Roman Republic. At the theatre, locals and visitors alike were able to watch performances of drama and song. Today its ancient edifice in the rione of Sant’Angelo, Rome, once again provides one of the city’s many popular spectacles or tourist sites.