Building a single-occupancy home over a former water cistern was the starting point of the project. The site, subsequently altered over time, reached its final configuration circa 1955. It has two levels, facing south, and has remained unaltered since then. The site is part of a low-density suburban environment, which belongs to a development model distinctive of peripheral areas, characteristic of the first third of the 20th century as the summer stays residential areas in the mountain range of Madrid. It contains typical scrubland vegetation, increased with non-native but suitable species, conditioned by the region´s dry continental climate. It was initially an underground cistern connected to a well. It presented informal floor plan geometry, probably due to the adaptation to a rocky ground. The unevenness of the ground propitiated the surfaced of the southern side of the fabric, which adopted the image of a strong retaining wall that confined, on this side, an upper paved platform where is located the well head, and which was occasionally used as space for celebrations. When the cistern no longer fulfilled its mission, it started to be used as a warehouse for all sort of utensils, but without any other adaptation than an entrance aperture. The interior constructive and structural configuration was then revealed. This was the first re-appropriation, yet the place continued maintaining its initial ethos as an accessible exterior space, that hides, underground, a warehouse. The final re-appropriation occurred with the transformation of the site in order to address the commission.
Neither the immediate environment nor the toponymy is modified; quite the opposite, the pre-existing is accepted as a possible trace pattern (the curved glass façade follows the trace of the former step to be maintained…). On the former paved platform emerges a perched object that moves forward and overhangs facing south over the novel empty space produced by the unevenness of the terrain. The inferior ground level is slightly lowered in order to, with the creation of a new enveloping wall, create a veranda that is placed outside the former platform atmosphere, and that now boasts being, at once, interior and exterior. The upper floor of the house occupies the new prefab-timber volume sitting on top of a new metallic structure that does not interfere structurally with the old massive structure. This volume shapes a big open space that works simultaneously as living/dining room and kitchen, communicating the house with the common garden. The lower level, partially buried, includes the intimate spaces, fragmented rooms of retreat, opened to a patio and to the aforementioned porch veranda facing a pre-designed artificial landscape. The building envelope of the new volume has been designed with a high degree of thermal insulation concerning a distribution of blind/open planes that optimizes natural lighting and cross ventilation, in addition to those other conditions particular to the pre-existing cistern volume (massiveness, natural ventilation, distribution of apertures, spaces semi buried and `cave or grotto effect´), which reinforce the energy concept of the house, fundamentally based on passive measures.