The Temple of Serapis is located on the Commercial Agora near the western gate. Construction on the temple began in the 2nd century AD and there are indications that suggest it may never have been fully finished.

The temple would have been built for the Egyptian merchants that often visited Ephesus for trading. It is well documented fact that Ephesus had strong commercial ties with the Egyptian port city of  Alexandria. The Egyptian merchants would have visited Ephesus often to exchange wheat, Egypt’s major export at the time, for other commercial items.

The temple would have been accessed either through a 24 meter wide and 160 meter. long stoa, or covered walk-way, along the western gate, or through a stairway on the south-west corner of the Agora. The main structure of the Temple of Serapis was a 29 meter wide square with thick walls to support the heavy stone roof. The entrance was supported by 57 ton granite columns that held a thick metal door. The door had to be opened and closed with a the help of a series of wheels located underneath.

Inscriptions in the temple indicate that it was a serapeum, a religious institution constructed for the worshipers of the Cult of Serapis.  This god was a combination of the aspects of Osiris, god of the afterlife, and Apis, god of strength and fertility. Serapis was a popular humanized god during the Ptolemaic Greeks of Alexandria. Archeologists found two statues inside the temple made from granite that would have been imported from Egypt. These statues represented the Egyptian god Serapis and the Ephesian huntress goddess Artemis. The two statues stood together with a garland as a symbol of peace.

The remains of a baptisterium in the eastern corner of the temple suggests that it was converted to a church during the 4th century AD when Rome converted to Christianity.