Buenos Aires, Argentina
True flea market lovers can hoof it over to the gritty, lively Mercado de San Cristobal, a massive market that once housed the best fresh fish dealers in Buenos Aires. Located just off the standard tourist circuit, the massive market building is just a dozen blocks from the picturesque Mercado de San Telmo, the classic covered antique market, and several blocks south of Plaza Congreso and the national congress building. Inside, treasure hunters will find stalls of used clothing, furniture, knick-knacks, army regalia, and more. On weekday mornings, fresh produce stalls burst with fruits and vegetables and butchers carve out choice cuts of beef and poultry; Saturdays the fish is back in full force so if seafood is your thing, head over.