Before doing renovation or new construction in the 1600-year-old town of Brno (officially settled in 1243 but occupied since the 400s), it is standard practice to do a preliminary archeological dig, but what they found under Jakubske namesti or “St. Jacob’s Square” was a surprise to everybody.

Some 50,000 skeletons were stuffed under the square into a medieval charnel. The bones were once piled in neat rows, but at some point water and mud had flooded the gigantic underground ossuary and jumbled the thousands of bones.

The bones, thought to be from the 1600 and 1700s, are believed to have been dug up from an old cemetery to make space for more burials, as is the case with most of the ossuaries and catacombs in Europe. It is the sheer amount of skulls, bones and skeletons here, second only to the Catacombs in Paris, that make the Brno ossuary especially significant. It is clear that many of the people died of various diseases which can be seen in the coloration of the bones themselves. Though all the bones are tinted yellow — having never been exposed to sunlight — the extra-yellow ones likely indicate death from cholera, while the owners of the red-tinted bones probably died from the plague.

The ossuary opened to the public for the first time in June of 2012.