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Yelp
This market is located right by the old Stock Exchange or Bourse building, right in central of Lille - the Bourse building itself is quite a spectacular sight, being of Flemish Renaissance design and style. The building itself is well worth visiting and taking a selection of photos of.
Back to the market in the inner courts, I found there to be a mix of stalls selling flowers and second hand books (in French unsurprisingly). Did not find any bargains here myself, but that is down to my limited French, and not really a reflection of the deals to be had for the books.