Lambach Abbey

Lambach Abbey in Upper Austria was of course where Hitler as a little boy learnt to serve Mass and sang as a choirboy.

Famously there's also a carved swastika in the sacristy, though it doesn't actually have anything to do with "the" swastika, which was already the symbol of the Nazi Party before Hitler came along. (The one in Lambach Abbey is actually two crossed carpentry nails and comes from the coat-of-arms of a former abbot.)

Needless to say, Hitler's claims in Mein Kampf about how as a boy at Lambach he revelled in the wonderful liturgy and had a filial respect for the abbot (as an authority figure and leader, of course!) can be taken with more than a pinch of salt. In any event, the abbey, which had survived the "secularising" depredations of the Holy Roman Emperor Joseph II in the Eighteenth Century, was eventually dissolved and turned into a state school as part of Bormann's Operation Klostersturm. (The monks returned after the War though, and according to their website they are still there today.)