Crowning the hill, with stunning city panoramas from its terrace, this superb example of late-19th-century French ecclesiastical architecture is lined with magnificent mosaics. From April to November, free 30-minute discovery visits take in the main features of the basilica and crypt; otherwise, 90-minute rooftop tours ('Visite Insolite') climax on the stone-sculpted roof. Reserve tickets in advance online for the latter.
Shutterstock / Jeroen Fortgens