This was indicated as the sanctuary for the Egyptian Gods. Some drain pipe or such.
The sanctuary of the Egyptian Gods. In Priene, worship of the Egyptian gods (Isis, Sarapis, Anubis and Harpocrates) is attested by inscriptions since 200 BC. These also tell us that chickens were given as sacrificial animals and that all sacred hymns had to be sung by an Egyptian priest. Sanctuaries for Egyptian gods were popular in most regions of the Mediterranean from the 3rd century BC onwards. This was, on the one side, encouraged by the expansion of the Ptolemaic empire in Egypt, on the other side, faith in Sarapis and Isis offered a possible afterlife that was otherwise unknown in the Greek set of beliefs.
During the 3rd century BC the area held large residential buildings. This is testified by the mighty ashlars belonging to the court of the well-preserved portal house. One or two centuries later the sanctuary was erected, visible remains belong to the 1st century BC or AD. In the middle of the courtyard a Roman-Italian style antae temple was erected on a podium, which was accessed by a flight of stairs. Access to the temple enclosure was enabled by a Propylon in the north-west.
A functional change in Byzantine times is shown by numerous graves in the south of the south of the then abandoned sanctuary.