The immense Mycenaean fortress of Gla, which cannot be identified with a town known from written sources, was situated on an island in the Copaic Lake in Boeotia. Today, the lake has been drained and the old city has become more accessible. Still, it rises almost forty meters about the surrounding fields.
The ("cyclopic") walls, made of blocks of natural stone, are 2¾ km long, which makes Gla a very big city. It was larger than, for example, Mycene or Tiryns. The pottery can be dated to the Late Helladic IIIB period, which is more or less identical to the thirteenth century BCE.
Inside the fortress, the remains of a large building (a palace?) and a market place with long work- and store-rooms have been identified.
The pottery suggests that the site was again in use in the Byzantine age.