The 2,186 stalls of the flea market and the 879 premises on its streets, with the goods the city authorizes on each one. From the city register, not from word of mouth.

El Rastro is not one uniform block: the city register splits the goods street by street. If you are after something specific, which end you come in by matters a great deal.
The 18 streets of El Rastro, one by one · The 13 trades and where each one concentrates

El Rastro is the city's biggest street market, not its only one: 33 street markets with 3,683 stalls, 45 municipal market halls and 1,396 licensed street-vending pitches, in three separate city files.
Three things that are in city documents, but scattered across a bulletin, a thousand-page fiscal ordinance and a layer of a map service. Read and worked out here.
The rules of El Rastro, with their sources · The 119 premises, one by one
If you come to El Rastro
If you have a business here

No noise. One notice when we add something worth the trouble, and nothing else.