Powder Tower

The Powder Tower in Mainz was the Martin Tower of the Fortress of Mainz used as a powder tower for about the last 50 years of its existence. It gained particular notoriety due to the Powder Tower explosion on the afternoon of November 18, 1857.
The Martin Tower originated in the Middle Ages and was the outer Gaust Tower; it was originally called the outer Gaub Gate. When, around 1660–1670, under Johann Philipp von Schönborn, the Martin Bastion became part of the contiguous fortress of the city of Mainz and the two other Gaub Gates were demolished, the outer Gaub Gate was preserved as the Martin Tower. The building was used as a stock house, that is, a military detention house. The Gaust Gate, built after 1670 and demolished in 1896, replaced the old Gaub Gates.

Wikipedia