Mont Saint Michel
Granite, 80 m high tidal island with a monastery church. The difference in height of the sea level at high and low tide is about 15 m, the most in Europe. So either the mountain is surrounded by quicksand, or it "floats in the sea". The low tide exposes the seabed up to a distance of 15 km.
Tomas Neuwirth, Czech Republic, Jesenik