Second prize in a private competition. The building is based on the concept of energy efficiency. In Seville, the sun is a crucial factor that provides mild winters and very hot summers. We proposed a compact and heterogeneous building, with three main features that give it personality and allow bioclimatic regulation. 1 - CIRCULAR PERIMETER The circle encloses the largest area in the minimum perimeter. The space has the same gradient. 2 - INTERIOR COURTYARD THERMAL REGULATOR. The inner courtyard is conceived as a centripetal element in the building that has a thermal regulatory effect on the ambient and mood of its dwellers. This space is crowned with a lightweight cover that protects it against the sun and rain, provides natural ventilation and holds thermal and photovoltaic solar panels. 3 - FACADES. Its exterior responds to the solar incidence. It creates a facade whose transparency varies according to its orientation, acting as a natural regulator, optimizing the cladding and protection, depending on their level of exposure. The greater the exposure, the smaller the cladding apertures are.