A view looking south at the main altar and behind it the Purgatorium. In the lower right side of the image, the banister leads up to the Temple of Isis.
The Purgatorium was a roofless structure covered with plaster. In it is an underground chamber where water from the Nile River was stored for use in rituals associated with the Egyptian deity, Isis.
The current structures were built after the earthquake of A.D. 62 and thus were only 17 years old when Pompeii was buried by the eruption of Vesuvius in A.D. 79. The well-preserved temple was one of the first discoveries at Pompeii in 1764!