Stockholm's oldest church, dating to the late 13th century when Franciscan monks built a monastery on the little islet of Riddarholmen, just off Gamla Stan. For nearly 400 years it served as Sweden's royal burial church — almost every Swedish monarch from Gustav Vasa onward is interred here, their sarcophagi filling the nave in a way that makes the space feel more like a dynastic crypt than a church. The cast-iron spire, a replacement for the medieval one lost to lightning in 1835, is one of the most recognizable points on the Stockholm skyline.
Open to visitors in summer. The island itself is worth a stroll at any time of year — the view back across the water to the city hall and Gamla Stan is one of Stockholm's best.