One of the most unusual things to see in Greece has to be the Thessaly Plain, where bizarre rocky outcrops are capped by the centuries-old monasteries of Metéora. On the UNESCO World Heritage list, six of the monasteries are open to the public.
You need to climb up several flights of stone steps carved into the rocks to reach each monastery, and inside, you'll find flickering candles, religious icons, Byzantine frescoes, and burning incense. Opening hours vary, and to see all six monasteries, you need to spend at least one day in the area.