Gla (Mod. Gr. Γλας, ancient name unknown) is a Late Helladic fortress and likely administrative centre built on a rocky outcropping (once an island) in the north-east quarter of former Lake Copais in northern Boeotia.Gla—also occasionally “Glas” in archaeological literature—is a fortified site built on an outcropping in the north-east quarter of former Lake Copais, about 1.5 km south-east of the modern village of Kastro, formerly Topolia, Boeotia. While Kastro/Topolia has been identified with the site of Greco-Roman Copae, the ancient name of Gla is unknown, though it has been the subject of much inconclusive speculation. The modern name is derived from Arvanitic goulas (γουλάς), also the name of a locale near Evangelistria above Haliartus on the south side of the Copaic Basin (cf. Albanian kullë from Turkish kulle “tower,” particularly “watchtower”). This appellation is reported to refer particularly to the extant ruins on Gla’s summit. The site has also been called Palaiokastro (“Oldcastle”) in modern times. The nearest village’s Slavic place name Topolia (“Poplar Place”) was officially abolished in the mid-.