As the Vatican prepares to display bones it believes to be those of St Peter, we explore an amazing series of jewelled saints' remains from southern Germany, Austria and Switzerland. The skeletons were found in 1578 when some of the catacombs of Rome were opened up, containing the remains of the city's early Christian community. Over the next couple of hundred years, some of the skeletons, identified as saints' remains, were sent north across the Alps to replace relics destroyed in the Protestant Reformation. To mark their newfound status, they were festooned with an extraordinary assortment of jewels, cloth of gold and other precious fabrics, and are still objects of veneration. Paul Koudounaris tracked them down for his book Heavenly Bodies, published by Thames & Hudson and available through the Guardian bookshop