The house at Cerro del Aire was the first home built by Miguel Fisac, and he did it at a crucial time in his life: a year after he had left the Opus Dei and a year before getting married to Ana María Badell. At the time, the hill on which it is located was in the middle of a piece of land that then belonged to the municipality of Alcobendas. From this hill one could see towards the south, in the direction of Madrid and behind a grove of cedars and lime trees, the convent that the architect was building for the Dominican Fathers. From the start he conceived it as an extendible house: “the beginning of a house, with the idea of adding rooms”, and he did this at least three times, as the clear and simple distribution of the main spaces always allowed it to grow without altering the basic concepts that articulate this architecture. All of it is developed on a horizontal plane built by making the slope flat, and orientating its central access nucleus, living room, and dining room towards the south through an impressive, large, ceiling to floor window which occupies one whole side of the room. Behind this, towards the west are the service and kitchen areas, while the bedrooms are in a line in the side orientated towards the east, with the articulating intermediate piece of a patio-garden where a great granite rock appears to rise to the surface. It was a way of somehow reintroducing Nature in the centre of the house, as was done in Zen gardening in Japan, which Fisac had so admired on his travels to the Far East. The garage is forward from the facade line of the living room, on the west side, taking advantage of the slope to open on a lower level which allowed an auxiliary bedroom to be placed above it. The house reminds us of American constructions from the Fifties by Frank Lloyd Wright, Pierre Köenig or Richard Neutra, whose work Fisac got to know during his trip to the USA in 1955 and with whom he maintained a friendship for many years, although in its synthetic realism it is closer to the intentions of the Nordic architects who had left such a deep mark on him during his trip in 1949. Building a house in Madrid comparable to those in Los Angeles at a time of low industrialization and limited material catalogues is a challenge that Fisac took on in this house and other constructions and compensated for with his work and inventiveness based on production of inventions that were often handcrafted. The construction of the house is mainly of granite masonry used as the load bearing system, and also walls of bare bricks. It also has some metal pillars that support a thin slab of concrete. Some ceilings and walls have panels of natural wood, the same material used for the carpentries, while the floors are paved with continuous strips of ‘Sintasol’ synthetic linoleum, which overall create interiors which are economical and practical to use, with a warm and natural look that is very easy to maintain because each material shows its real appearance, and paint, when used, is restricted to the service areas. This realist and unprejudiced sense, so characteristic of the Nordic world, also extends to the furniture, formed by some pieces that Fisac was experimenting with at the time, and which he had commissioned and craft produced himself to study their possible industrial manufacture, and it also includes woollen or jute curtains and carpets, woven in their natural colours, as Oriol Bohigas and Josep Martorell clearly explained in issue number 3 of the magazine ‘md’ in 1963. With time the house grew on the north side, beyond the children’s playroom, where a prefabricated workshop was attached where he did some of his building experiments with concrete, later applied in the completion of his study, -located on an adjacent plot, and other works carried out with flexible formwork.