In late 1248, William II of Villehardouin, ruler of the Frankish Principality of Achaea, captured Monemvasia, the last remaining Byzantine outpost on the Morea. This success was soon followed by the submission of the restive Tsakones on Mount Parnon, the Slavic Melingoi tribe of Mount Taygetos, and the inhabitants of the Mani peninsula, thereby extending his sway over all of Laconia and completing the conquest of the peninsula, which had begun in 1205, in the aftermath of the Fourth Crusade. Laconia was incorporated into the princely domain, and the young prince passed the winter of 1248–49 there, touring the country and selecting sites for new fortifications such as Grand Magne and Leuktron; finally, near his residence of Lacedaemon (ancient Sparta), on a spur of Mount Taygetos, he built the fortress that came to be known as Mystras.