The Temple of Augustus (Templum Augusti or Aedes Divus Augustus) was built by Tiberius (and maybe Livia) in honour of Augustus. Tiberius might not have finished it, or might not have dedicated it, in which case it was finished and/or dedicated by Gaius (Caligula). The remains of the temple are probably to be found under the modern buildings behind the Basilica Julia, but it has not been excavated.
Earlier the Temple of Augustus was identified with the Annex of Tiberius’ Palace on the Vicus Tuscus, behind the Temple of Castor and Pollux and at the foot of the Palatine Hill. These buildings are from the period of Domitian, and have nothing to do with the Temple of Augustus, which probably stood just across the Vicus Tuscus.
- LacusCurtius: Platner: A Topographical Dictionary of Ancient Rome
LacusCurtius: Hülsen: Il Foro Romano – Storia e Monumenti
(Text in Italian)