Gla (Greek: Γλα), rarely Glas (Γλας), was an important fortified site of the Mycenaean civilization, located in Boeotia, mainland Greece. Despite its impressive size, more than ten times larger than contemporary Athens or Tiryns, Gla is not mentioned in the Iliad.
The site is located on a limestone outcrop or hill that jutted into Lake Kopais (now drained) or formed an island within it. The flat-topped outcrop rises up to 38m above the surrounding area. It measures circa 900 x 575m (at the widest point). The ancient name of the site is unknown, it is unclear whether it is one of the Boeotian places named by Homer (some scholars suggest that Gla is Homer's Arne). The scholarly designation "Gla" is from the Albanian word for fortification; the modern local population calls the site Paliokastro (Greek for "ancient fortress").
Excavation revealed much detail about the fortification walls (which were always visible) and, on the interior, remains of buildings from the Mycenaean period. The fortification encloses an area of nearly 20 hectares, about 10 times as much as the Mycenaean citadels of Athens or Tiryns.
The walls surrounding Gla were about 3 m thick, and 2.8 km long, enclosing about 235,000 square meters of land. These massive walls were made from Cyclopean masonry. In many locations they are built directly on the cliffs that form the limit of the outcrop. It had four gates, an unusually high number for a Mycenaean fortification, in the north, west, south and southeast. Elaborate built ramps led to the gates. The fortification can be dated to early Late Helladic III B, that is, circa 1300 BC.
Within the walls, there was thought to be a palatial complex, but recent evidence has pointed in the direction of a military establishment with lots of storage space. Of all the space that in enclosed within the walls of Gla, there are very few permanent structures, and they take up less than a quarter of the space inside the walls. Some of this empty space possibly was used to house temporary structures, especially in times when there was construction and draining in progress.
Much of the area within the walls is vacant, leading archaeologists to believe that it served as a refuge for farmers in the area of Lake Kopais in the event of attack. It is suggested that the land dominated by the citadel of Gla served as the "bread basket" of the Mycenaean world. This is supported by the fact that Lake Kopais, the largest lake in southern Greece, had been drained by a system of dams and canals (one of the most astonishing achievements of prehistoric engineering) at about the same time as the erection of Gla, producing a large fertile plain. The drainage system collapsed from destruction or neglect at or after the end of Mycenaean Civilisation; in Classical Antiquity, the lake existed again. It was drained a second time in the 19th century.
The system comprised two large canals that met about 1 km north of Gla. These canals combined covered over 50 km in length, and collected water from the Boeotian Cephissus and Melas rivers and redistributed them into areas where the water flowed out to sea easily.
The most striking interior feature is a large L-shaped building, often described as a "palace". It is in the north of the site, which is subdivided by several internal walls in this area. The "palace" is located on an artificial terrace and consists of three wings. Each of the wings contains mostly very small rooms, arranged in groups of six and accessed by corridors. At the two ends of the L, there are similar arrangements of rooms resembling the megaron complexes known from Tiryns, Mycenae Dimini and Pylos. Nevertheless, the lack of several typical features of other Mycenaean palaces, namely of a "throne room", a (circular) hearth and a "bathroom" casts some doubt on the designation of the structure as a palace.
Two further Mycenaean architectural complexes were found further south, in the area of the so-called "agora", which is separated from the "palace area" by a wall. The two complexes are parallel to each other (north-south orientation) and have similar plans. In each, a long corridor links buildings in the north and south of the complex. They are subdivided into small rooms. There is no scholarly consensus on their function. Suggestions include use as barracks, storage spaces/distribution centres, or workshops. The storage theory is supported by the discovery of large amounts of carbonised grain (probably burnt during the destruction of the site) in one of the buildings.
An interesting feature of the buildings at Gla is the discovery of fired pan and cover tiles, suggesting that some Mycenaean buildings already featured pitched, tiled roofs similar to those known from Classical antiquity.
There is some evidence that human occupation of Gla was not limited to the Mycenaean period. For example, the site yielded pottery from Neolithic and Byzantine times. It does not, however, appear to have been occupied during the Archaic-Classical Greek and Roman periods.