Here you are in Barcelona when you suddenly get a hankering for...  oh, I don't know...  Damson plums.  Where the heck can you get Damson plums in Barcelona?  Oh, that's easy!  Mercat St. Josep!  You can get anything at Mercat St. Josep.  Spices, fruits, vegetables, honey and preserves, kitchen equipment, car insurance, wine, beer, spirits, beef, pork, lamb, goat, and if you could get camel or elephant there, I wouldn't be at all surprised.

Just walk north on La Rambla until you see the market entrance on your left.

There are acres and acres of stalls operated by an army of independent vendors.  After you've been a Barcelonan for a few decades, you'll develop a list of your favorites and be able to make a bee line for their location.

This is why Mercat St. Josep is packed wall-to-wall with shoppers from opening to close.