San Isidro is the patron saint of the peasants and laborers and is also the patron saint of Madrid. Tradition has it that on May 15th the people of Madrid are to make a pilgrimage to San Isidro's meadow to celebrate his day and to drink the holy water of his fountain in his hermitage's patio. Madrid's biggest "fiesta" is celebrated yearly starting on the Friday before the 15th and running until the following Sunday, 9 days of Saintly jubilee throughout the Comunity of Madrid.
Gigants (people on stilts) with "cabezudos" (big, satirical papier mache heads) parade around the city center, usually on the first Saturday afternoon of San Isidro.
Weekend partying is centered day and night around the Plaza de las Vistillas, Plaza de San Andrés and Puente de Segovia in the Austrias neighborhood, near the Plaza Mayor. At night, bars set up shop on the street, or "chiringuitos." Good luck elbowing your way through the hordes to get a "mini," the Spanish term for a huge plastic cup of mojito, beer, cocktail or mixed drink
San Isidro has been an official festival in Madrid since 1947 and while technically the festivities run from May 8th to the 15th, like good Spaniards they stretch the fun and always start earlier and end later. The festival actually begins with the Mayor's speach on the Friday afternoon prior to the 15th and ends with the ever popular Cocido Madrileño or public Cookout.