Pergamon was an ancient Greek city in Aeolis, today located 16 miles (26 km) from the Aegean Sea on a promontory on the north side of the river Caicus (modern day Bakırçay). It became the capital of the Kingdom of Pergamon during the Hellenistic period, under the Attalid dynasty, 281–133 BC. Pergamon is cited in the Book of Revelation as one of the seven churches of Asia. Today, the main sites of ancient Pergamon are to the north and west of the modern city of Bergama in Turkey.