The Alqueva Reservoir on the Portuguese-Spanish border is the largest artificial lake in Europe. It lies amid a gentle hilly landscape, surrounded by forests and open grassland. Hidden amongst this natural scenery is a house penned by the renowned Aires Mateus in Lisbon. This building was dug into a hill on the south-western shore of the lake by architect brothers Manuel and Francisco Aires Mateus.

Taking advantage of the topography, you can barely see the large building from the west and certainly not from the air. The only visible features are the steep staircase, two circular atriums and the basin at the top. From the other side, you can see a raw concrete body that appears to shield a dom. Here, the concrete roof protrudes out, covering a generous open space and living area behind it. The opening in the roof provides light which streams right into the heart of the house, the terrace. Inside the house, two bedrooms are illuminated by the brightly white painted inner courtyards.

The result is a building that is both reduced and elegant, yet seamlessly integrated into nature. It’s raw, concrete and daring forms also brings a touch of science fiction to the otherwise wild and romantic Portuguese landscape. Readers of the ArchDaily website were so impressed by this structure that they voted it “Building of the Year 2020”.