Pergamon
Pergamon's other notable structure is the great temple of the Egyptian gods Isis and/or Serapis, known today as the "Red Basilica" (or "Kızıl Avlu" in Turkish), about south of the Acropolis at (39 7' 19" N, 27 11' 1" E). It consists of a main building and two round towers within an enormous "temenos" or sacred area. The temple towers flanking the main building had courtyards with pools used for ablutions at each end, flanked by stoas on three sides. The forecourt of the Temple of Isis/Sarapis is still supported by the Pergamon Bridge, the largest bridge substruction of antiquity.
Pergamon
The Madradağ aqueduct was a ceramic pipe with a diameter of 18 cm which already brought water to the citadel from a source over 40 kilometres away in the Madradağ mountains at 1174 m above sea level in the Hellenistic period. Their significance for architectural history lies in the form of the last kilometres from the mountains through a 200 metre deep valley to the Akropolis. The pipe consisted of three channels, which ended 3 km north of the citadel, before reaching the valley, and emptied into a pool, which included a double sedimentation tank. This pool was 35 metres higher than the summit of the citadel. The pipe from the pool to the Acropolis consisted of only a single channel - a lead pipe pressurised to 200 mH2O. The water was able to cross the valley between the pool and the citadel with the help of this pressurised conduit. It functioned as a communicating vessel, such that the water rose to the height of the citadel on its own as a result of the pressurised pipe.