What the Viennese have done to their big-ass cathedral, the Stephansdom, is typical of the city's abject surrender before the conquering armies of tourists. In order to provide a better view from one tower, they've bolted an acrophobia-inducing steel catwalk to the outside of the tower. Up the 200+ steps of the other tower one finds a gift shop.
Underneath the cathedral are the catacombs, and if there isn't already an action-thriller set in Vienna that ends up down there, there ought to be. During various outbreaks of Black Death, Vienna would dig a deep hole in the square next to the Stephansdom and just toss the dead in. Then, for a while, they used the catacombs as inexpensive tomb space. Every time the place filled up, they'd carefully disassemble the skeletons, stack the sorted bones up in neat piles -- femurs with femurs, skulls with skulls -- and free up some space.
Plus, there are some Habsburg emperors and churchmen down there, but they're all resting in nicely sealed stone caskets, which isn't quite as ghoulishly fascinating.