The Imperial Crypt holds about 150 Habsburgs in ten cellar rooms under a Capuchin friary. Each generation saw what the one before had built and answered it. Maria Theresa had a double tomb cast in tin, big enough to need its own domed room; a few steps away her son Joseph II lies in a riveted copper chest with one small cross. Beyond them the rooms grow plainer, and one built in the 1960s has bare concrete walls shaped to look like earth in an open grave.
Empress Anna paid for the friary in her will and died within months, before the foundation stone was laid; her coffin and Emperor Matthias's were carried down in 1633. After that the vault kept running out of room. When Ferdinand III died there was no space left, so his coffin was set crossways over the founders' two and the first extension was dug. The last coffin came down in 2023. Nothing stands behind glass, so you read the lettering at arm's length.