Otto-Wagner-Kirche in Vienna

You're standing at the Kirche am Steinhof, high on a hill on the western edge of Vienna. Start with that dome. It shines with gold leaf and you can spot it from far across this part of the city. It looks a bit like half a lemon, which is how the hill got its nickname, the Lemoniberg. This is the church of a psychiatric hospital. Architect Otto Wagner built it between 1904 and 1907, and it's counted among the most important Art Nouveau churches in the world.