The castle-town of Platamonas, a meso-Byzantine monument (10th century AD), rests atop the hill of the seaside town of the same name. The castle controlled the strategic eastern crossing of the mountain. The castle is one of the most well-preserved castles in the north of Greece, built on top of the ancient fortified settlement of Irakleio. Its present-day appearance is of Frankish construction, with some more recent repairs. It was completed after 1204 by Boniface I, Marquis of Montferrat, who reigned as king of Thessaloniki. In the following years, Platamonas found itself at the forefront of many occupations and conquests by the Byzantine Empire’s claimants up until 1386, where it fell into the hands of the Ottomans. Over the years that ensued, Platamonas became the focal point of numerous sieges and takeovers, as many claimants of the Byzantine Empire fought for control over it. In 1386, it eventually fell into the hands of the Ottomans. The outer fortification perimeter of the castle is polygonal in shape, and the wall’s height varies from 7.5 to 9.5 meters, depending on the altitude of the terrain. On the north-eastern side stands the acropolis, surrounded by a second perimeter. Situated within the acropolis is the octagonal central tower of the castle, which stands at approximately 20 meters tall. It was constructed in the 15th century and has been remarkably well-preserved. Excavations inside the castle brought the ruins of Byzantine churches to light, which had been renovated in the 17th century. The castle was deserted by its residents during the 19th century and was only used for military purposes during certain periods, right up until World War II. After extensive maintenance and promotion by the archaeological service, the castle of Platamonas stands today as one of the most significant medieval landmarks in the region surrounding Olympus. It attracts many visitors and serves as the venue for various events of the Olympus Festival.