There are some very interesting catacombs, with remains of over 11,000 people, under Saint Stephan's Cathedral.
During the bubonic plague outbreak of 1735 thousands of corpses were placed in pits that were dug in the floor of the crypt. The smell, unfortunately, wafted up into the cathedral and made religious services impossible. In order to get rid of the odor, prisoners from the local jail were sent down to scrub the flesh off the rotting corpses and stack the bones into neatly ordered piles.
Another section of the catacombs contains large jars with organs, mostly intestines, from deceased members of the royal family. Apparently, one of the jars recently had a rather odoriferous leak and it took several days before anyone was willing to go into that part of the catacombs to deal with the situation.