The mountain that stands north of Greece is Mt. Olympos. This mountain stands on isolation, situated on the borders of Thessaly and Macedonia, and is one of the most interesting botanical localities of the Balkans. There is also the Mt. Falakro, situated near the City of Drama and Mt. Athamanon. You can see more mountains that are situated to the northern Greece from http://www.greekmountainflora.info/Pages/Northern%20Greece.htm.