Poised at the apex of the hill like a grande dame in crinolines, this odd-looking 19th-century basilica has become one of the city’s most famous landmarks. After France’s defeat in the Franco-Prussian War, prominent Catholics vowed to build a church consecrated to the Sacred Heart of Christ as a way of making up for whatever sins the French may have committed that had made God so angry at them. Since 1885, prayers for humanity have been continually chanted here (the church is a pilgrimage site, so dress and behave accordingly). Inspired by the Byzantine churches of Turkey and Italy, this multidomed confection was begun in 1875 and completed in 1914, though it wasn’t consecrated until 1919 because of World War I. The white stone was chosen for its self-cleaning capabilities: When it rains, it secretes a chalky substance that acts as a fresh coat of paint. Most visitors climb the 237 stairs to the dome, where the splendid city views extend over 48km (30 miles).