Walking down the Samariá Gorge
We were in Crete, with a spare day and we wanted to hike. While the bus system is a gigantic pain, it was well worth it for these gorgeous views.
Samariá Gorge is the biggest gorge in Europe. It's a 16km long though the hike is 18km and hiking it takes you from 1250m above sea level to sea level.
At the Gates it becomes 4m wide and 300m tall. Seeing the Gates and then walking through is a breathtaking experience.
There are plenty of rest stops, toilets, water stops and goats unique to the area :)
If you're in Crete, it's worth the daytrip.