Well, it's not gurgling here and this isn't an ordinary downspout. It's a gargoyle and it is located on the famous Sainte-Chapelle chapel, just around the corner from the Notre Dame de Paris. It is a marvelous combination of stained glass, stone and air. It's not on the "normal" tourists stops so you'll have to make special efforts to get there. Interestingly, its inside the main judicial complex in central Paris so you'll also have to go through metal detectors.
One of the architectural features of many Gothic churches are the carved downspouts, known as gargoyles. And the sound of water rushing through the monster's mouth was described as a "gurgle," a word derived directly from the name of these conduits.