Orvilos is a mountain on the border of the regional Units of Drama and Serres, on the borderline of Greece and Bulgaria; it extends beyond the borders of Greece to the side of Bulgaria at Blagoevgrad Province. It is connected in the east with Mount Falakro, in the south with Mount Menikio, and in the west with Vrontou Mountains. Its highest peak is Tsolias (or Ali Botous) with an altitude of 2,212 meters.

Orvilos features alpine and subalpine meadows, with rich flora and fauna. The beautiful 18-km trail to Tsolias starts from the village of Katafyto and the banks of the artificial reservoir lake of Katafyto.