Greece's Mount Parnassus is a mixture of adventurous possibility and cultural intrigue: a rare combination not to be taken for granted. On the historical/mythological side, its highest peak (Liakoura) was claimed to be the home of the muses while, to the southwest and less controversially, the Temple of Apollo marks the site of the legendary Oracle at Delphi. The latter location alone could keep you occupied for a full day but, if you've come to Parnassus looking to experience Greece's rugged natural beauty, you won't be short on things to do.
Mid-May through late October, when the peak isn't snow covered, 4x4 drives and hikes up to Liakoura's well marked summit (2,457 m) provide stellar scenery over southern countryside, extending as far as the Gulf of Corinth on a clear day. Come winter, Parnassus is home to two of the best ski/snowboard destinations in Greece: Kellaria and Fterolaka. They can reportedly get crowded come the holiday season, but I doubt there's much you can do about that. Overall, for a destination that has a little bit of everything to offer, this is a mountain that's hard to top.