We stopped in Durnstein on a river cruise and while many of the cruisers were walking the tourist shops, three of us climbed to the top of the ruins. It's a fun, steep climb, with nice views of the Danube Valley all the way up. But, persevere--the views from the top are simply incredible. Evidently, Richard the Lionheart was imprisoned there during the Crusades and the ruins are fun to walk around.
There is NO shortcut to get to the top, so you have to be reasonably fit to make this climb. The steps are irregular, so be careful on the way up and down. I think you should allow at least 30 minutes for the climb to the top and nearly the same on the way down.
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