It sounds like a horrible nightmare: human bones stacked in patterns on the floor, their skulls lining the walls and staring, gaping-eyed, at visitors. It’s no nightmare, though: in churches, cathedrals and underground chambers all over the world, the bones of millions of dead greet visitors. The grisly rooms, known as ossuaries, serve as the final resting place for human remains, often due to overcrowded cemeteries. They exist for different reasons, but they all hold a sort of macabre fascination for us, the living. These seven stunning examples of ossuaries remind us that life is fleeting, but some part of us can live on in this world.

Easily one of the most incredible collections of human bones in the world, the Sedlec Ossuary in the Czech Republic is unlike anything else. The small church rests at the outskirts of Kutna Hora and is filled with the mortal remains of more than 40,000 people. The origins of the “Bone Church,” as it’s commonly known, are nearly as interesting as the array of bones. In 1278, an abbot named Henry