Pergamon
Pergamon lies on the north edge of the Caicus plain in the historic region of Mysia in the northwest of Turkey. The Caicus river breaks through the surrounding mountains and hills at this point and flows in a wide arc to the southwest. At the foot of the mountain range to the north, between the rivers Selinus and Cetius, there is the massif of Pergamon which rises 335 metres above sea level. The site is only 26 km from the sea, but the Caicus plain is not open to the sea, since the way is blocked by the Karadağ massif. As a result, the area has a strongly inland character. In Hellenistic times, the town of Elaia at the mouth of the Caicus served as the port of Pergamon. The climate is Mediterranean with a dry period from May to August, as is common along the west coast of Asia Minor.
Pergamon
For the altar's construction, the required flat area was skillfully created through terracing, in order to allow it to be oriented in relation to the neighbouring Temple of Athena. The base of the altar measured around 36 x 33 metres and was decorated on the outside with a detailed depiction in high relief of the Gigantomachy, the battle between the Olympian gods and the Giants. The frieze is 2.30 metres high and has a total length of 113 metres, making it the second longest frieze surviving from antiquity, after the Parthenon Frieze in Athens. A 20 metre wide staircase cut into the base on the western side leads up to the upper structure, which is surrounded by a colonnade, and consists of a colonnaded courtyard, separated from the staircase by a colonnade. The interior walls of this colonnade had a further frieze, depicting the life of Telephus, the son of Heracles and mythical founder of Pergamon. This frieze is around 1.60 metres high and thus is clearly smaller than the outer frieze.