Rue de la Gaîté red light district (Quartier Rouge) is a small (300m) street in the Montparnasse area of Paris. You can see the location on my Paris map
and I have ringed it in this photo that I took from the top of the Montparnasse Tower
(Tour Maine-Montparnasse). This sky scraper by the way gives fantastic views of the whole city and has a large viewing area. It's quite expensive at around 13 Euros which is more than the Eiffel Tower
. At the top of the photo is the Montparnasse Cemetery (Cimetière du Montparnasse).
Rue de la Gaîté is quite respectable and only has a small number of adult shops. The rest of the street is made up with restaurants, cafes, theatres, bars and hotels. Theatres include Theatre de la Gaite-Montparnasse, Théâtre Montparnasse, Petit Théâtre du Montparnasse, Bobino, The Italian Comedy and Théâtre Rive Gauche (see below).
The nearest metro stations to this area are Gaîté on line 13 and Edgar Quinet on line 6.