Opuntian Locris consisted of a narrow slip upon the eastern coast of central Greece, from the pass of Thermopylae to the mouth of the river Cephissus. The northern frontier town was Alpeni, which bordered upon the Malians, and the southern frontier town was Larymna, which at a later time belonged to Boeotia. The Locrians, however, did not inhabit this coast continuously, but were separated by a narrow slip of Phocis, which extended to the North Euboean Gulf, and contained the Phocian seaport town of Daphnus. The Locrians north of Daphnus were called Epicnemidii, from Mount Cnemis; and those south of this town were named Opuntii, from Opus, their principal city. On the west, the Locrians were separated from Phocis and Boeotia by a range of mountains, extending from Mount Oeta and running parallel to the coast. The northern part of this range, called Mount Cnemis, now Talanda, rises to a considerable height, and separated the Epicnemidii Locri from the Phocians of the upper valley of the Cephissus; the southern portion, which bore no specific name, is not so lofty as Mount Cnemis, and separated the Opuntian Locrians from the north-eastern parts of Boeotia. Lateral branches extended from these mountains to the coast, of which one terminated in the promontory Cnemides, opposite the islands called Lichades; but there were several fruitful valleys, and the fertility of the whole of the Locrian coast is praised both by ancient and modern observers. In consequence of the proximity of the mountains to the coast there was no room for any considerable rivers. The largest, which, however, is only a mountain torrent, is the Boagrius (), called also Manes () by Strabo, rising in Mount Cnemis, and flowing into the sea between Scarpheia and Thronium. The only other river mentioned by name is the Platanius, a small stream, which flows into the Opuntian gulf near the Boeotian frontier: it is the river which flows from the modern village of Proskyná.