The decoration of this church are real bones.

This picture’s taken in the Sedlec Ossuary, Kutna Hora, in the Czech Republic not too far from Prague.

Long story short, holy man brought back some holy dirt from Jerusalem, threw it down on the church grounds. From then on everyone wanted to be buried there. The grounds were already full from some gnarly battles, so the priests dug up the non-stinky bones and made pretty decorations with them to clear room for fresh burials…as you do.

Seclec Ossuary