I get the impression that this is kind of like the McDonalds of Spain.
So cheap. On Tuesdays they have a "everything for 1 euro" day. You can feed and quench the thirst of two people well for 7 euros.
Even on regular days, the most expensive montadito will only run you 2.50 euros I believe. Many choices (100). They have a sampler in case you have no idea what to order (us the first time). Really cheap and refreshing beer and tinto de verano (my favorite new drink from this trip to spain). Get the Jarra size. Its not as big as the name implies.
Order up at counter. They have these nice little sheets at the tables where you can mark what you want so you dont forget (each of the 100 montaditos is assigned a number). Once you get up to the counter, they'll still ask you to read off what you want. Your food will be ready within a few minutes.
This location is right in the middle of things. 2 blocks from Plaza Mayor, 2 blocks from Puerta del Sol. Two floors. read more