commemorative plaque to La Alcantarilla and Fuentes de San Pedro

Commemorative plaque to La Alcantarilla and Fuentes de San Pedro stands in Madrid's La Latina district, at Plaza de los Carros, right by Costanilla de San Pedro and the church of San Pedro el Viejo. It's a small marker set into the paving, but it points to one of the oldest water stories in the Spanish capital.

Where exactly is the plaque located?

The plaque sits in Plaza de los Carros, in the heart of La Latina — one of Madrid's oldest quarters, laid out back when the city was a fortified outpost within the Caliphate of Córdoba's territory. The square lies close to where the medieval Puerta Cerrada once stood, one of the gates of the original walled town, and next to the church of San Pedro el Viejo, among the oldest in Madrid.

What does the plaque actually commemorate?

It marks the discovery of a qanat — an underground water system dating from Madrid's Islamic period (Al-Andalus). A qanat is a network of tunnels and shafts that carries groundwater by gravity, without pumps, a technique that supplied the city from the medieval period well into the modern era, before the Canal de Isabel II was built in the 19th century. Archaeological work under the square's paving uncovered a stretch of this centuries-old infrastructure.

Why the double name — "La Alcantarilla" and "Fuentes de San Pedro"?

The two names cover different stages of the same story. "Fuentes de San Pedro" were the springs that, in the days of Alfonso the Wise, gave their name to a stream running through this spot — it rose near an older church that stood before today's San Pedro el Viejo. "Alcantarilla" (literally a conduit or drain) refers to a water channel built at those springs, considered one of the oldest known water conduits in Madrid.

How did the area change over the centuries?

By the late 13th century, baths fed by the springs were run by a Moorish woman named doña Xani; their conduits were later used to build a fountain known as "del Alcantarilla." In the 16th century, the architect Juan de Herrera — the man behind the plans for El Escorial — had the stream buried underground, along the route now followed by Calle de Segovia. Some historians even link the name "Madrid" to the Latin "Matrice," the term for the main, "mother" underground watercourse of the city.

Who put up the current plaque, and when?

The plaque was installed by the Fundación de Cultura Islámica after archaeological surveys confirmed the qanat beneath Plaza de los Carros. Madrid's city council chose not to enclose the site under glass for display, opting instead for an information panel with a QR code linking to material on the city's historic "viajes de agua" — the channels that once supplied Madrid's water. Irene Suárez, the foundation's outreach coordinator, oversaw the project.

Frequently asked questions

Is the plaque easy to find while walking around La Latina? Yes — Plaza de los Carros sits on the usual walking routes through La Latina, a few minutes from Puerta Cerrada and Plaza Mayor, so it's an easy stop to add to a visit.

Can visitors actually see the qanat itself? No — the site wasn't turned into a museum display or opened to visitors. The infrastructure remains underground, and the plaque with its QR code stands in for a physical exhibit.

What makes a qanat different from an ordinary well? A qanat is a connected system of tunnels and vertical shafts that moves groundwater by gravity rather than pumping — a technique brought to Madrid during the Islamic period and used for centuries.

Why does this spot matter for Madrid's history? It ties together the city's oldest documented water systems — from the medieval springs and baths through Juan de Herrera's engineering work to the qanat found beneath the square — showing an unbroken, centuries-long history of how Madrid supplied itself with water.