Holy Mount Athos is a self-governing and autonomous area in Greece. It covers the whole third peninsula of Halkidiki, which is around 50 kilometres long and 8 to 12 kilometres wide, and has a total size of 330 square kilometres. In the centre of the Mount Athos peninsula, a lengthy variety of hills and mountains culminates in the 2,033-meter-high Mount Athos.
The border between this monastic state and the rest of Greece is a line traced from Francocastro on the western coast to Cape Arapis on the opposite coast, going close to the slopes of the peak “Megali Vigla” (Megas Zigos).
Prior to the third century B.C., the peninsula of Athos was home to several tiny Greek settlements, mostly Chalkidaean and Eretrian colonies. Sani, Ouranoupolis, Thisson, Kleones, Dion, Akrathos, and Olofixos were the most significant.
These settlements eventually decayed or were destroyed.