Hovering lightly alongside a hillside of Linz, the villa designed by the Austrian firm of Najjar and Najjar is a statement on materials and at the same time a celebration of lightness and air. There are elements long familiar to modernism-the pure planes of glass and travertine, the open interior arrangement, the adherence to a few, carefully chosen materials, in this case, aluminium, stone and glass, that are allowed to have not only a functional but an aesthetic presence. But then there is a flourish and a calm, dynamism and stillness in this house that takes modernist precepts to a new level of engagement. Though they are known for their experiments with kinetic architecture and futuristic yacht design, the architects deny that they had any specific theme or model in mind when this project was conceived. The basic mechanics of the 420 sq m house follow a logical sense of order and progression. Working away from the hillside, there is a dugout basement, then, a concrete foundation and walls support a steel structure that is hung with glass and clad in aluminium. The solidity of the hillside, the grounding of the house is emphasized by the use of stone, the dugout sections and a series of pools - reflecting pools at the entrance and a neat rectilinear swimming pool at the rear. The entrance side of the house on the north-west corner sits on a level surface of the hill and presents a solid facing of limestone; while the lower ground floor, which offers an open view over the medieval and modern townscape of Linz, is clad in a series of glass panels, some of which can be fully opened to light and air. From earthy beginnings, the structure then nearly takes flight with the glazed southeast façade and the angular roof shapes that have the profile, the sense of movement, of a large bird or a streamlined jet. This uplifting quality, of what is actually a very large and complex roof structure, is induced by the cantilever, which extends 9 metres at its farthest reach, and by the row of clerestory windows, another gesture from the modernist handbook. But in this design the band of invisible structure means much more than a subtle introduction of natural light. The clerestory is the visual gap in the solid walls that creates the illusion of the weighty roof actually being a free-floating cap. It is one of many instances of visual sleight of hand that allows a large solid structure to appear bright and weightless. Fortunately for the architects, the clients, a young couple with children, embraced that rare adventurous spirit, not only conceding to bold ideas but embracing them with zeal. Their commitment brings to mind the figures of Fritz and Greta Tugendhat, the young couple who allowed Mies van der Rohe the freedom to create the audacious structure in Brno in 1929 that is now one of the most famous buildings of Modernist design. As it dances with similar principles, this house bows to that earlier version but then takes up its own daring rhythm. The cantilever of the roof is a spectacular sweep that wraps around the upper level of the house and, in so doing, creates another roof for the ground floor volume, all the while allowing transparency to prevail. For all of the house’s poetics, however, a clear logic applies not only to the materials but also to the arrangement of the spaces, which are articulated by partial and whole changes in levels in a mostly open-plan interior. The entrance level includes an enclosed family room, and then stairs lead upwards a full level to an open gallery space and bedrooms, so that the private rooms are signally separate. Downwards, one is led to the glazed garden elevation where the kitchen/dining area opens to a walnut-decked terrace that maintains the connection of this room with the outdoors. A few steps below is the glass-walled living space that encompasses a wide terrace with a swimming pool. These rooms enjoy an uninterrupted view to the southwest, from where natural light enters and warms the interior in winter. (Passive solar gain is significant in winter while shading is effective with the change of the sun’s angle in summer.) A garage and spa area are situated in the basement level directly below the entrance, while another few steps down the hill gives onto a floor devoted to office and creative studio space as well as guest accommodation. The play with levels keeps spaces distinct without making many enclosures, and allows the main public areas to remain open, permeated by light and movement. Chosen for its durability and reflective quality, the aluminium cladding on the roof has a gentle sort of reflection that is at home with the travertine and stone and with the glass and pools of water. But while aluminium provides a suitably gentle sheen, the architects were not content to display only broad planes. The roof structure is punctured with louvered openings over the entrance and terrace that mirror the pattern of the travertine panels and allow sunlight to break up the mass. Whether it was intentionally modeled or not, the gentle undulation of the roof with these delicate louvered sections also brings to mind the graceful skeletal structure of wings.