There’s Trajan’s Arch and Marble Arch, the Arch of Constantine and Napoleon’s Arc de Triomphe. You can ride to the top of the biggest of them all, the 630ft (192m) high Gateway Arch in St Louis, or, in southern Spain, stare amazed at hundreds of intersecting horseshoe-shaped arches in the hypostyle hall of what was once the Great Mosque of Cordoba.