Basilique Saint-Sernin in Toulouse

You're standing at the Basilica of Saint-Sernin, one of the largest Romanesque churches still standing in Europe. Start by looking up at the bell tower rising over the middle of the church. It has five tiers. The lower three, with their round arches, date from the twelfth century. The top two were added in the thirteenth, and the spire only in the fifteenth. Notice anything odd? The tower leans slightly to the west. That's why, from some angles, the spire seems to sit crooked on top.