On a pine-covered summit overlooking the sprawling city of Nice, Mont Gros, a 19th-century observatory, is a local icon. Built by Charles Garnier (famous for his Paris Opéra design) in collaboration with Gustave Eiffel (yes, that Eiffel), the monument has inspired film location scouts and is popular with local couples who come to take in the stunning view of the city together. The observatory is still an active science laboratory focusing on astronomy, astrophysics, and geoscience. The original 18-meter-long lens is responsible for finding 2,000 previously unrecorded double stars. There are two-hour guided tours on Wednesdays and Saturdays year round, with a more frequent schedule during school holidays.