The ancient city of Pergamon was inscribed on the UNESCO World Heritage List in 2014. It is the only capital from the Hellenistic period that combines traces of the Hellenistic, Roman, Eastern, Roman and Ottoman periods. It is considered the most prominent example of Hellenistic urban planning with its monumental architecture, the Temple of Athena; It is the steepest theater of the Hellenistic period, the library, the great altar of Pergamon, the temple of Dionysus, the agora, the gymnasium, and the system of high-pressure water pipelines are the most prominent examples of the planning system and architecture of this period.