The Temple of Jupiter Optimus Maximus ("Temple of Jupiter Best and Greatest on the Capitoline"), also known as the Temple of Jupiter Capitolinus, is dedicated on this ides of September. Marcus Horatius Pulvillus, one of the consuls this year, is chosen by lots to perform the dedication ritual.

Located on Rome's Capitoline Hill, this is the city's most important temple. According to Roman tradition, Lucius Tarquinius Priscus vowed to build it in return for victory over the Sabines. It is dedicated primarily to Jupiter and his companion deities, Juno and Minerva, but shrines to Terminus and Juventas are also incorporated into the structure.

It is believed that the original temple measures almost 60 x 60 m (200 x 200 ft), though there is some debate and disagreement on these figures. This original structure will burn down in 83 BCE during the civil wars, and a replacement temple isn't dedicated until 69 BCE. That one will burn down in 69 CE when Vespasian has to fight to enter Rome and become emperor. A third Temple of Jupiter Optimus Maximus will be dedicated in 75 CE and only lasts until 80.