Is the Montmarte flea market open on Sundays and how far is it from the Moulin Rouge
According to the website they are open Sat & Sun from about 9:30 to 18:00. I'm not very good at estimating city distances but I would say about 2km (walking or driving). Someone like Ed who's good at that sort of thing may give you more accurate info. By metro it's about 7 metro stops with a change at Barbes-Rochechouart (line 4 from Porte De Clignancourt, then line 2 from B-R to metro stop Blanche). I'm sure there's probably buses too but I'm not familiar with the routes around Montmartre.
Assuming this isn't a trick question: 1. Wow your pals with the knowledge that neither the Moulin Rouge nor the Saint Denis flea market are actually in or on Montmartre. 2. It's about a mile and a half walk, mostly flat, around the west side of the butte. It's undistinguishedly boring and the sidewalks are narrow so you have to do a lot of threading, figure at least a half hour. Nancy's description of the metro lines and switch looks right - - I've never done it. 3. The street vendors start pulling down mid-afternoon on Sunday. The book stalls and such in the buildings might remain open longer, beats me. I'd also guess that the street vendors are in business well before nine since their crap was set up Friday night and all they have to do is pull the tarps. I've seen people nosing around at the junk well before eight.
Wherever it is, it will be fun. It's amazing how French junk looks so much better than American junk.