Riegersburg

You're standing at Riegersburg Castle, high above the little town of the same name in the Austrian state of Styria. Take a look at the rock beneath your feet. This isn't just any hill. It's what's left of a volcano. What you see is the solidified core of a large volcano that probably went extinct around two million years ago. The summit sits at 482 metres. And the castle itself? It was built from the dark basalt of that very rock.