Palacete de Carlos María de Castro, Madrid

Palacete de Carlos María de Castro is a historic townhouse in Madrid, standing on Calle de Fernando el Santo in the Almagro neighborhood. It is one of the few surviving residences from the earliest days of the Ensanche, the 19th-century expansion that shaped the modern center of the Spanish capital, and it was built by the very architect who designed that urban plan.

What is this place?

The house was designed and built in 1864 by Carlos María de Castro, the engineer and urban planner behind the Ensanche de Madrid, the grid of streets that defined the city's modern layout. He built the residence for himself on Fernando el Santo, a street that had only just been laid out at the time, and it went on to set the tone for the townhouses that gradually filled this part of the new district. In 1878 the building was remodeled by the architect Tomás Aranguren for its new owner, the Count of Heredia-Spínola, the military officer and politician Luis Martos, who had also served as mayor of Madrid.

What will you see?

The building has two main floors, an attic level, and a semi-basement. The street-facing side presents a formal facade, while side entrances lead to a garden and a glazed sitting room traditionally known as the "estufa" (literally, a hothouse or conservatory). The garden-facing elevation is flanked by two small corner towers, giving the whole structure a residential, almost countryhouse-like silhouette that is rare to find today in this part of the city. The palacete remains privately owned, currently by businessman José María Aristrain, a shareholder in the steel group ArcelorMittal, and it is not open to the public.

How do you get there?

The palacete sits in Almagro, a neighborhood within the Chamberí district, in a quiet area dense with late-19th and early-20th-century buildings. The easiest way to reach it is by metro: the closest stations are Alonso Martínez and Colón, both a short walk from Fernando el Santo. The area is also well served by city buses running along Paseo de la Castellana and Calle de Génova, making it an easy add-on to a day exploring central Madrid.

What else is worth seeing nearby?

Almagro is one of the most elegant corners of the Ensanche, filled with Art Nouveau and eclectic-style apartment buildings, foreign embassies, and refined residences from the turn of the 20th century. A walk along streets like Fernando el Santo or Zurbano reveals architecture from the same era as the Castro palacete, though few buildings have retained such a distinctive, individual character. Nearby, it's worth continuing on to Paseo de la Castellana, one of the city's main avenues, and the area around Plaza de Colón.

When should you visit?

Since the palacete is privately owned and has no regular visiting hours, the best plan is simply to walk through the neighborhood at any time of year — spring and autumn offer the most comfortable weather for exploring Almagro on foot. Pairing the walk with nearby museums and viewpoints in the Chamberí district makes for a well-rounded outing.

Frequently Asked Questions

Can you go inside the Palacete de Carlos María de Castro? No, it is a private residence and is not open to visitors — you can only admire it from the outside.

Who designed this palacete? It was designed and built by Carlos María de Castro, the engineer and urban planner responsible for the Ensanche de Madrid plan.

Why does this building matter to Madrid's history? It was one of the first houses raised in the newly laid-out Ensanche district and became a model for the residences that followed in the area.

What is the easiest way to reach the Almagro neighborhood? The metro is the most convenient option — get off at Alonso Martínez or Colón station, both a short walk from Fernando el Santo.