Rouen Cathedral

The west front Claude Monet painted in a series of 28 canvases, and standing in the square where he worked, watching the light change on the stone, is the best way to understand them. The south tower is the Tour de Beurre, the Butter Tower, said to have been paid for by wealthy believers who bought the right to keep eating butter in Lent. Above it all rises a cast-iron spire completed in 1876, at 151 meters the tallest in France. Inside lies the heart of Richard the Lionheart. Admission is free, as befits a working church, though some areas close during services.