Burg Kreuzenstein in Leobendorf

You're standing at Burg Kreuzenstein, high above the village of Leobendorf, just north of Vienna. Take a look around first. You're about a hundred metres above the Danube here. Off in the distance, the river squeezes through the Wiener Pforte, the Viennese Portal, a narrow gap in the landscape. On the far bank, roughly straight across from you, sits another castle: Burg Greifenstein.