It is hard to walk among great numbers of human remains without feeling like a trespasser. The dead are their own nation, their own tribe, and whatever these pale creatures once had in common with the rest of us departed when they breathed their last. They leave behind bones and memories, and since, in our modern Western culture, we are uncomfortable with the dead and their whispers of mortality, we make sure that those bones are placed where no one will have to look at them again. We bury them deep, or burn them to ash and cinders. They are the dead, and they are no part of us. In time, even the memories fade as those who knew them follow them from this world into the next, so that, in the end, only the ashes remain and only the bones persist.

But there are places where the dead remain above ground in greater numbers, gathered together in silent conclave, and to enter their presence is like walking in on a conversation that we have interrupted by our intrusion. For the dead are not, in the end, so different from us. We have their skulls beneath our skin, their bones in our backs, and they speak to us quietly, friend to friend, as we gaze upon them. They tell us that as they are now, so we too will be. They remind us that all things will pass, the good and the bad, and we should cherish the former and endure the latter as best we can.

And then the dead return to their own conversations, and leave us to consider what we have been told by them.

There are such places in the world.

Sedlec is such a place.

From the first time that I visited the ossuary of All Saints Church on the outskirts of this little town in the Czech Republic, I knew that Sedlec was different, and the more I began to rummage around in its past, the more fascinating it became. It is one of those places where, for a brief period in history, religion, politics, great wealth and great violence all intertwined. The few square miles upon which they came together are now marked by a pair of cathedrals, by a monastery filled entirely with tobacco executives, by glum suburbs and Communist-era apartments.

And by a church furnished with human bones.

Initially, there is something unsettling about Sedlec. It’s probably the collision that occurs in the mind between the structures themselves and the materials used to create them. After all, that is clearly a chandelier hanging from the ceiling, and those are candelabra beneath it, yet the items in question are made not from brass or crystal but from human remains. Take the candelabra: the candles stand on skulls, their lower mandibles missing and their upper jaws each gripping a horizontal bone. They are inset into a kind of pyramid of marble, one skull above the next in three vertical rows of six, the pyramid tapering almost to a point and topped by another skull. There are four pyramids in all, set in a square, and above them is that most extraordinary chandelier.

The chandelier is reputed to contain an example of every bone in the human body. Once again, the candleholders are set into skulls, this time a circular arrangement of about ten, each skull at the end of one arm of the chandelier and each carefully balanced on what appear to be human pelvises, chains of bones connecting them to the central column of the chandelier. The entire arrangement hangs from a stone ceiling garlanded with more skulls and bones. It is breathtaking yet profoundly disturbing, a work of art created from the dead as a message to the living.

This, then, is Sedlec. It forms the basis of my new book, The Black Angel, but its contents, and its history, are so strange that my own fictions pale by comparison. In addition to the chandeliers and candelabra there are also ceremonial urns from bone, and monstrances with a skull where the Host, the bread transformed into the body of Christ, should be. There is even the immense coat of arms of the Schwarzenberg family – who paid for much of the ossuary’s long restoration – assembled from the remains of the dead, rendered in such perfect detail that the artist recreated from bone a bird pecking out the eye of a Turk on the family’s crest. Four great free-standing pyramids of skull and bone, the earliest of the ossuary’s monuments, dominate each corner. Over 40,000 bodies were used to decorate this place, a process that began in the 16th century and continued until the 19th, starting with the stacking of those pyramids by a half-blind monk and ending with a woodcarver named Frantisek Rint signing his name in bone upon the ossuary wall.

But how did all these bones come to be here? The simple answer is that a lot of people wanted to be buried in this now almost forgotten outpost of what was once the Holy Roman Empire. The Cistercian monastery at Sedlec was very wealthy and very well-known, due in no small part to the discovery of silver on some of its lands, and the presence nearby of the mining centre of Kutna Hora. Legend tells that Jindrich, an early abbot of the Cistercian monastery at Sedlec, brought back with him from the Holy Land a sack of soil which he scattered over the cemetery. The cemetery came to be regarded as a piece of the Holy Land itself, and people from across Europe were brought for burial in its earth, alongside plague victims, fallen soldiers and the local dead. The 14th-century Zbraslav Chronicle records that, in one year alone, 30,000 people were interred at Sedlec. That’s almost 600 people every week, and the cemetery itself isn’t very big. Finding somewhere to put them all required considerable effort, energy and ingenuity.

The crucial thing to understand about medieval cemeteries is that they were not like our own modern, neatly laid-out graveyards. Most of the bones used to furnish Sedlec came from the great common graves of the poor that would have dominated the centre of the cemetery. These were little more than ditches, 30ft long and 15 or 20ft across, into which the dead were cast sewn up in their shrouds, sometimes as many as 1,500 in a single pit covered by a thin layer of dirt, their remains easy prey for wolves and the grave robbers who supplied the anatomists. As one ditch filled, another older one was opened up and emptied of its bones, which were then stored wherever space could be found, whether within the main church building, against its sides, or in the arcades and porticoes along the cemetery walls. It mattered little to most people where their bones ended up just as long as they remained in the vicinity of the church, and it was common to see human remains lining the walls, or the porch, or even stored in small chapels specially designed for the purpose, which is how the ossuary at Sedlec came into being.

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