At the top of the hill, on Costanilla San Andrés, the Plaza de la Paja was the most important square in medieval Madrid. The plaza's jewel is the Capilla del Obispo (Bishop's Chapel), built between 1520 and 1530; this was where peasants deposited their tithes, called diezmas—literally, one-tenth of their crop. The stacks of wheat on the chapel's ceramic tiles refer to this tradition. Architecturally, the chapel marks a transition from the blocky Gothic period, which gave the structure its basic shape, to the Renaissance, the source of its decorations. It houses an intricately carved polychrome altarpiece by Francisco Giralta, with scenes from the life of Christ. To visit the chapel (Tues. 9:30–12:30, Thurs. 4–5:30) reserve in advance (91/559–2874 or firstname.lastname@example.org).
The chapel is part of the complex of the domed church of San Andrés, one of Madrid's oldest, which was severely damaged during the civil war. For centuries the
church held the remains of Madrid's male patron saint, San Isidro Labrador (now with his wife's remains, at the Real Colegiata de San Isidro, on nearby Calle Toledo). St. Isidore the Laborer was a peasant who worked fields belonging to the Vargas family—the 16th-century Vargas Palace forms the eastern side of the Plaza de la Paja. According to legend, St. Isidro worked little but had the best-tended fields thanks to many hours of prayer. When Señor Vargas came to investigate, Isidro made a spring of sweet water spurt from the ground to quench his master's thirst. A hermitage (Ermita de San Isidro), now on Paseo de la Ermita del Santo, west of the Manzanares River, was built next to the spring in 1528. Every May 15 there's a procession followed by festivities in the meadow next to the hermitage. In olden days, the saint's remains were paraded through the city in times of drought.