Inexpensive, crowded and very small. This tiny little taco bar is great for a quick bite and a beer. In general mexican food in spain is much more authentic then the texmex you'll find in other countries but this place is especially so.
They have a good selection of tequilas and the mecheladas are also pretty good.
Calle de las Fuentes, 11
28013 Madrid Madrid
Spain+34 915 59 87 11