Held every Sunday from 9 AM to 3 PM, the El Rastro Market is the biggest open-air flea market. With roughly 3500 stalls, there is plenty to keep you busy. If you’re done shopping, you can enjoy the street artists or duck into one of the restaurants / cafes lining the streets to have a beer and tapas.
Gaudeamus Cafe in the Lavapiés neighbourhood of Madrid - The Gaudeamus Café is on top of the Escuelas Pías, an old university. It's beautiful and quirky and offers amazing views over the city. The restaurant is on the fourth floor, but don't use the lift or you'll miss the building – it's full of history.