Lamia castle stands at the highest part of the town, on the summit of a rocky hill. It dominates the surrounding area and controls the valley of the river of Spercheis as far as the Malian gulf, and the pass that leads through mount Orthrys to Thessaly. It is a highly important monument and bears direct witness to the history of the town. Archaeological excavations of previous and recent years have demonstrate that the site was occupied from at least the Early Bronze Age (2700 - 2300B.C). The fortified acropolis was the centre of the defences of Lamia in the Classical and Hellenistic periods and was linked with the fortifications of the lower city. The earliest part of the fortification has polygonal masonry and dates from the 5th B.C., when Lamia became capital of Malis. The surviving parts of the ancient fortifications include parts of the base of the north-west and south-east corners and of the west side, which reveal that the original plan of the acropolis was probably not very different from the one that is now preserved. Other parts are preserved with isodomic masonry of trapezoidal or square blocks at various points of the base of fortification wall. In the present form, the fortification has the form of a right - angled triangle in plan, and its inner surface ends in crenelated battlements. It was built by the masters of the fortress at various times, who employed the building styles of their day based on the core of the fortifications of the ancient acropolis. Its entire extent is preserved in excellent condition as a result of its continuous use and succesive repairs. The north and south sections are founded on the bedrock, which reaches a height of approximately 10m in the south-west corner. The east and west sides stand on steep slopes, in accordance with principles of ancient fortifications works. The length of the perimeter is approximately 600m. and the heigth of the wall varies with the configuration of the terrain. The highest and most imposing points are the north-west and east corners, which rice to 13m. and 11,7 respectively. The masonry is 1,35m. thick on average, and the top takes the form of crenellated battlements with a passageway 0,90 to 1,20m. wide. The defensive wall has two gates, one on the south-east and one on the north-east. The south-east gate, which was called "Sidera" (Iron) was the main entrance. On the exterior it has an arched lintel of poros, surmounted by a relieving arch of brick. A small stone staircase links the gate with the passageway on top of the wall. The north-east gate also has a semi-cylindrical brick lintel. To strengthen the fortificacion wall, towers were erected at intervals, mainly close to the gates, at the corners of the wall, and in general at all vulnerable points of the fortifications. The internal area of Kastro is divided into three parts by two transverse walls. The division is probably owed to the Franks or the Catalans. The three sectors were at different levels, providing an inner line of defence if the main gate was breached. The north section (Akropyrgio) is the highest and served as the last refuge of the defenders of the Kastro. The south dividing wall of the section is preserved in good condition and has atop it part of the passageway and battlements for the defence of the besieged. Entrance to the Akropyrgio was by a gate with an arched lintel of poros block.