Eduardo Lello
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Definitely not for every tourist. It is a huge market, filthy, unorganized and with a certain sense of being somewhat dangerous. I didn't feel unsafe but we were followed several times by locals, certainly not very well intended.
But it is an adventure, an experience, and I loved it. I certainly recommend it, but only if you feel like you have the guts for it. (you see every part of an animal's body on display there!)
The produce there is amazing and you can literally find just about everything that you need, from a to z!
It's Colombia and Cartagena at its best, and it's nice to go out of the walled city and live an authentic experience. Also there's loads of food stalls that you can buy and try local food of!
Keep your wallet and documents at home (take just some cash in small bills), don't take your expensive camera with you and don't flash your cellphone around, keep your wits about your surroundings there, and you should be fine. It also helps if you know some Spanish.