Northwest of Athens near Litochoron, the stone pillar of Mount Olympus (9,571) is a great free climb. Typically, plan about 2 days for the ascent. Start in the village of Litochoran and follow the Enipeis River gorge. Next twist your way through the dense forest to a refugio called Spilios Agapitos for the night. Then hike up Kaki Skala (Evil Stairway) along a deep chasm to the plateau heading to the summit.
Overall, Mount Olympus is the 1st most popular hiking trail of all 3 hikes in Greece.