The Temple of Trajan, or Trajaneum, was a magnificent structure built in honour of emperor Traian, hence its name, and located on the highest point of the citadel (acropolis) of the ancient city of Pergamum, or Pergamon, near the eastern coastline of Minor Asia.

Construction of the temple and the surrounding sacred precinct (Trajaneum), actually, commenced under the reign of Trajan himself around 114 AD but was completed later during the time of his successor Hadrian in the first half of the second century AD, serving as a venue for the cult of both Roman emperors.

Facing west, the temple was made almost entirely of white marble and stood on a high podium in the middle of a terrace that measured a good 68 x 58m laid out on a levelled slope, supported by a complex of eleven arched tunnels.

The building measured itself about 18m wide and lined up six Corinthian-styled columns at the front and back apiece as well as nine along either side with the altar situated at some distance towards the edge of the terrace.

Originally, the site was devoted to Jupiter Amicalis (or Zeus Philios in Koine, meaning ‘Jupiter/Zeus pertaining to friendship’) apparently extending a message of friendship by the ruling Romans to their subjects.

Most likely, nonetheless, that was no other than Egyptian Serapis, a merge of Osiris and Apis, since he was the king deity (Jupiter/Zeus) venerated across the city as further demonstrated by the Roman temples of the Serapium and the Red Basilica.