Galeries Lafayette Rooftop is a real time commitment — fit it in only if it's a priority.
Allow 30–45 min.
Two payoffs in one stop: the spectacular stained-glass dome over the shop floor, then a free rooftop terrace with the Opéra, Eiffel and Sacré-Cœur on the horizon. It's a department store, so it's busy and commercial, but the view costs nothing.