Trompe l’oeil or illusion painting depicting architectural details dating from 1499 on the façade of high castle, Füssen (Germany).

(via)

Edit: This is the High Castle in Füssen. Additionally, the more famous fairy-tale-like castle Neuschwanstein also lies in Füssen. The crazy king Ludwig II who built Neuschwanstein apparently spent some time at the this castle as a kid. (thanks propaedeuticist for the info!)