Capitolium

The Capitolium in Ostia Antica is a Roman temple standing at the northern end of the Forum with a height of around 17 meters. The structure features a 21-step staircase, vestibule foundations, and basement rooms with barrel vaults beneath the main temple floor.

The temple was built during Emperor Hadrian's reign around 120 AD as part of Ostia's development as Rome's principal port. Starting in the 15th century, marble materials were systematically removed from the structure, continuing into the early 19th century.

The temple honored the three deities revered in Rome's most sacred shrine, making it a symbol of connection between the port city and the capital. This religious arrangement reflected how Rome extended its most important cult practices to cities across its territory.

The temple is easily accessible from the Forum area with the ruins fully open to walk through and explore all levels. Sturdy footwear is recommended when navigating the staircase and basement areas to avoid slipping on ancient stone.

The marble threshold of the temple is remarkably large, matching in proportion the famous threshold of the Pantheon in Rome. This parallel shows how important architectural details were repeated between the capital's most sacred shrine and this provincial temple.