For me it has to be the bone church in Kutná Hora. In the 1800s a rich family acquired a church. They commissioned a wood carver, František Rint, to arrange the bones of tens of thousands corpses from the surrounding grounds (mainly mass graves of plague and war victims) into various things. They then decorated the church with them. Imagine bone chandeliers, and skulls and bones arranged like garland. The worst, Rint, arranged bones into the house crest that commissioned him. Somehow, I don’t think the family would like it if they had themselves or relatives remains arranged in these ways…