The Powder Tower is located in the Old Town of Prague. It was originally used as a fortress for the moat. It was later used to store gunpowder, so it was called the Powder Tower. In the 16th century, the king allowed the warlocks to study alchemy here, and in the 18th century used to store the sacristy of the Church of St. Vitus. It has now become a museum for exhibiting medieval art, astronomy and alchemy artifacts.