Spectacular views unfold from this 209m-high smoked-glass-and-steel office block, built in 1973. (Bonus: it's about the only spot in the city you can’t see this startlingly ugly skyscraper, which dwarfs low-rise Paris.) A speedy lift/elevator whisks visitors up in 38 seconds to the indoor observatory on the 56th floor, with multimedia displays. Finish with a hike up the stairs to the 59th-floor open-air terrace (with a sheltered walkway) and bubbly at the terrace's Champagne bar.

The tower also houses the city’s highest restaurant, Le Ciel de Paris.