Mihulka Powder Tower

This guide to Mihulka Powder Tower in Prague Castle turns a former cannon bastion into the site of an imperial obsession: Emperor Rudolf II's attempt to turn base metal into gold. It follows the two alchemists he funded, the smooth-talking Englishman Edward Kelley and his elder partner John Dee, a mathematician and adviser to the English queen, and the years of furnaces, vials and unmet promises inside these thick fortress walls. Look up at the tower's rounded shoulder, later nicknamed for its lamprey-like curve.