The Grössmunster is one of Zurich's famous four historic churches, and easily its most recognizable with its twin towers a distinguishing feature of the city skyline. (They haven't, however, been universally loved. Richard Wagner famously compared them to a pair of salt-and-pepper shakers.) The church is steeped in history having been established by Charlemagne and then in the 16th century serving as one of the centers of the Reformation, as Huldrych Zwingli formulated his theological arguments in an office here. The church's plain interior speaks to the legacy of Zwingli and it is a reformed church to this day. While the interior may be somewhat restrained, it includes important—and beautiful—windows by Giacometti and Sigmar Polke. Make sure to also visit the Fraumunster, which has stained glass windows by Marc Chagall.