This was used as a burial place by the Habsburgs from the 14th century to the 18th. In the middle of the 17th century, the custom began of using the Imperial Crypt at the Capuchin Church as a resting place for the bodies, while placing the hearts in a room off St. George's Chapel at the Augustinerkirche ( There's a website HERE. ) and the viscera in urns along the walls of the Archducal Crypt. You can see them in the picture above, though they were later moved to another room. The custom ended with the burial of the Archduke Franz Karl in 1878.