Pergamon or Pergamum was an ancient Greek city in Aeolis located 26 kilometres (16 miles) from the Aegean Sea on a promontory on the north side of the river Caicus (modern-day Bakırçay). Today the main sites of ancient Pergamon are to the north and west of the modern city of Bergama in Turkey. 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.