In the aftermath of the Battle of Actium (31 BC), Marcus Agrippa started an impressive building program: the Pantheon was a part of the complex created by him on his own property in the Campus Martius in 29-19 BC, which included three buildings aligned from south to north: the Baths of Agrippa, the Basilica of Neptune, and the Pantheon.[14] It seems likely that the Pantheon and the Basilica of Neptune were Agrippa's sacra privata, not aedes publicae (public temples).[15] This less solemn designation would help explain how the building could have so easily lost its original name and purpose (Ziolkowski contends that it was originally the Temple of Mars in Campo)[16] in such a relatively short period of time.[17]
It had long been thought that the current building was built by Agrippa, with later alterations undertaken, and this was in part because of the inscription on the front of the temple[18] which reads: