On Monday mornings there is a great flea market called Noordermarket which is fantastic for second hand retro clothing.
There is a general market on Saturdays on Lindengracht (parallel to Noordermarkt) selling everything from the mundane to the exotic and on Monday mornings the market specialises in cheap and cheerful materials.
Both are great places to mingle with the locals.
It's at the top end of Prinsengracht.
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