Katarina kyrka in Stockholm

You're standing at Katarina Church, on the island of Södermalm in Stockholm. Take a look at the shape of the building first. It's laid out as a cross, with that striking octagonal tower rising from the middle. That tower isn't the original, by the way. The first church went up between 1656 and 1695, designed by the French-born architect Jean de la Vallée. It's named after Princess Catherine, half-sister of King Gustavus Adolphus and mother of King Charles X Gustav.