I experimented a bit with post-processing on this and hopefully, it's not too much of sharpening.
Update: Thanks for the kind comments! In case you're interested: The staircase is at [Wikipedia:] Castle Hartenfels in Torgau. Here are other photos on flickr, on some you can see the staircase as well. It's called "Wendelstein" in German. Here's another flickr user's photo of the staircase seen from outside.