The Kaisergruft (or Imperial Crypt) is the last resting place of 146 members of the Hapsburg family, plus urns containing the hearts or cremains of four others. There are 107 visible sarcophagi that range in style from plain to very ornate.
Until far in the 18th century, the most common material for a sarcophagus here was a bronze-like alloy of tin, coated with shellac. The splendid tombs of the baroque and rococo eras are made of true bronze, a nobler and therefore more expensive material. Reforming Emperor Joseph II decreed simplified burial customs for the people, and introduced the use of lighter and cheaper copper into the Imperial Crypt, where it was then used into the 19th century. In the later 19th century a mixture of cast brass and bronze as well as silver-bronzed copper was adopted. Other metals were used only rarely, except for silver and gold plating on decorations.
Within the outer case lies a wooden coffin that is wrapped in silk (black with gold trim for rulers, red with silver trim for others). The coffin usually has two locks, the key to one is kept by the Capuchin Guardian of the crypt, the other is kept in the Schatzkammer of the Hofburg palace in Vienna.