A cemetery adjacent to the Church of St. James had existed on the present-day Jakubské náměstí (square) in the 13th century. And just like other cemeteries, it had been established within the city’s walls, which is why its subsequent expansion, albeit needed, was impossible. Its capacity soon proved insufficient with regard to the growing city and new burial methods had to be introduced: 10 to 12 years after the funeral the grave of the deceased had to be opened and their remains removed, only to make room for a new deceased person. The contents of the graves were stored in special underground ossuaries.
A three-room crypt was probably built for this very purpose right underneath the floor of the church in the 17th century. Initially the number of skeletal remains was increasing slowly but around the 1750’s skeletal remains from former church crypts started to form two big piles. The speed at which these rooms were filled often increased as a result of plague and cholera epidemics which claimed thousands of lives. The permanent lack of space for the bones led to the expansion of the ossuary in 1741. As it turned out, the most practical solution was the expansion of the new ossuary underneath the cemetery and its connection to the crypt of the church. However the new ossuary was filled out in only six years and the city administration started negotiations on further expansion via a connection with the Chapel of the Dead that was located nearby. However the digging of the connecting tunnel stopped half way through and the plan was never completed.
It was estimated they contained the skeletal remains of as many as 50,000 people. Analyses have shown that many of them fell victim to medieval plague and cholera epidemics, military operations during the Thirty Years’ War or the Swedish siege.
