Königstein Fortress

You're standing at Königstein Fortress, high above the River Elbe in Saxon Switzerland. This is one of the largest hilltop fortresses in Europe. Take a look at those walls. They run for 1,800 metres around the whole rock plateau, and in places they're up to 42 metres high, rising straight out of the steep sandstone cliffs. The plateau itself sits 240 metres above the river.