Start in the Plaza Mayor. Looking up at the playfully erotic mural on the Casa de la Panadería, which now houses the city tourist information center, exit under the arch to the far left and walk down Ciudad Rodrigo, and turn left. Across the street is the restored San Miguel market. As Cava de San Miguel becomes Calle Cuchilleros, look to the left for Botín, Madrid's oldest restaurant and a onetime Hemingway haunt.
The plaza with the bright murals at the intersection of Calle Segovia is called Puerta Cerrada, or Closed Gate, for the (always closed) city gate that once stood here. The mural up to the left reads, "Fui sobre agua edificada; mis muros de fuego son" ("I was built on water; my walls are made of fire"), a reference to the city's origins as a fortress with abundant springs and its ramparts, made of the kind of flint that creates sparks.
Nuncio widens, and on your left at No. 17 is the Taberna de Cien Vinos; sample some Spanish wine here. Opposite is the church of San Pedro el Viejo (St. Peter the Elder), one of Madrid's oldest, with a Mudejar tower. Bear right and walk the narrow and short Calle Príncipe Anglona to come to Plaza de la Paja. Down on the right is the ramped Costanilla de San Andrés, which leads to Calle Segovia and a view of the viaduct above. Look farther down Príncipe Anglona to see the Mudejar tower on San Pedro church; was reportedly built in 1354 after the Christian Reconquest of Algeciras, near Gibraltar.
At the top of Plaza de la Paja is the church of San Andrés and to the left of its entrance the Museo de San Isidro, a small municipal museum. Past the church, turn right after Plaza de los Carros into Plaza Puerta de Moros, then down Carrera San Francisco to visit the Basílica de San Francisco el Grande. Backtrack and turn left after San Andrés down Cava Baja, packed with bars and restaurants. Casa Lucio, at No. 35, is said to be a favorite of King Juan Carlos I; Casa Lucas at No. 30 is a great place to have imaginative tapas; and Julián de Tolosa at No. 18 has fine Basque fare. Continue across Puerta Cerrada and up Calle Cuchilleros to return to Plaza Mayor.