The Grossmünster with its distinctive twin towers is Zurich's most famous landmark. This Romanesque Protestant church was built in the 12th century on the site of an older Carolingian church. According to legend, Charlemagne founded the first secondary school here on the graves of the city's patron saints Felix and Regula. Highlights include the stained glass windows by Sigmar Polke, the Romanesque crypt, the choir windows by Augusto Giacometti, and the bronze doors by Otto Münch. Visitors can climb 187 steps to the Karlsturm tower for breathtaking panoramic views over the Old Town, Lake Zurich, and the Alps. The church is a significant historical site as Ulrich Zwingli began the Protestant Reformation in Switzerland here in 1519.