A Medieval Castle, it dominates the highest point of the town on a rocky hill with panoramic views of the picturesque Sperheios valley, the peaks of Oitis, Kallidromos, mythical Othryos, Parnassos, Gionas and of the Maliakos Gulf. In its well-preserved masonry is the historical continuity from the 5th century BC until the 2nd World War.
The Lamia fortification system consisted of two zones, the Citadel and the walls of the lower city. The preserved fortification enclosure is triangular and is well maintained due to ongoing repairs. Its perimeter reaches 600 metres and its height varies reaching 13 metres in the NW corner. The thickness of the masonry is on average 1.35m and ends in jagged ramps
The Castle has two gates, one at the SE, and the so-called “iron gate” through which connected with the lower city and another NE, which led to Orthry. Reinforced towers are raised near the gates, at the corners of the gates and in all the weak defence points. Inside the inner area, it was divided by two transversal walls into three parts. The northern section (ridge) is located higher and served as the last shelter of the defenders of the Castle. The plateau of the SW corner served as a bastion in the Middle Ages and had a reservoir. In the same place there are remains of a mosque.
During Ottoman times, a two-storey rectangular building was erected in the centre of the middle plateau, which was once used as barracks until the beginning of World War II. Nowadays, located within the castle area, Lamia Archaeological Museum, the 1st Ephorate of Prehistoric and Classical Antiquities and the Conference Centre are housed.