The project for a new glass gallery along Via Mazzini in the center of Perugia, covered by the Energy Roof, creates the entry point to the underground archaeological passage that connects the city center with the MiniMetro station Pincetto. A new public space and attractor takes shape. Its history, dynamic circulation flows, and urban liveliness defines the place.The paradigmatic design of the Energy Roof creates a distinctive and highly recognizable icon for the city, and a statement for aesthetic sustainability, corresponding with the ancient buildings of Via Mazzini. It marks the entrance to the underground archaeological passage leading through the history of Perugia. The underground passage is not only a shortcut between the city center and the arrival point of the MiniMetro station Pincetto, but also an exhibition space. Historical documents show the existence of the old Etruscan city wall in the area below Piazza Giacomo Matteotti which Coop Himmelb(l)au proposes to excavate as part of an underground public gallery space exhibiting the history of Perugia. Controlled views and look-out points make orientation easy. Openings in the ground of the Piazza Giacomo Matteotti visually connect the underground passage with the Energy Roof. The roof design is driven by the generation of energy for the city, and inspired by the shape of a propeller. While the orientation of the west wing is optimized in relation to solar radiation, the east wing captures wind. The roof consists of three layers: the energy-generating top layer, the structural layer in the middle, and a bottom layer composed of laminated glazing and translucent pneumatic cushions. The top layer includes transparent photovoltaic cells to generate electricity and shade. The orientation of the individual cells is generated and optimized by a computer- operated script. Furthermore, five wind turbines that are placed inside the structural layer are generating additional energy. Both the roof and the underground passage are energy self-sufficient. During the design process of the energy roof, a special focus has been put on using photovoltaic cells as functional and aesthetic elements. To maintain visual connections to the surroundings, we propose to use frameless glass elements with integrated transparent photovoltaic cells for the top layer of the roof. Shading, energy generation and architectural integration are combined into one element. The chosen geometry of the panels follows the overall shape of the Energy Roof, and curved lines made of photovoltaic cells are created. The photovoltaic elements are peeling off the surface and tilted towards the sun where the roof area is oriented to the North East. The resulting gaps are closed by passive glass panels which appear similar to the active panels. Considering the technological advances in 2009, this installation creates a photovoltaic energy generator with a performance of around 73 kWp. The annual output of 100 MWh provides a major contribution to environmentally friendly generation of energy. With the wind turbines and an additional performance of around 25 kWp a peak performance of around 100KWp is reached. Structural description – Preliminary The roof consists of three layers with the structural layer in the middle. The other two layers are the energy-generating top layer and the glazed bottom layer. In the summer, the east wing of the rotor blade-shaped roof captures wind, thus providing ventilation for cooling. The structure, therefore, has to be sufficiently open to drive the fresh air to the street level from above. The roof structure is approximately 80 meters long and supported by a tripod in the center. There are ten members connecting the roof structure to the tripod. It is about 16 meters wide at both ends while in the middle part, around the supporting points, the roof slims. The geometry of the structure is determined by crossed planes that are arrayed in a longitudinal direction. The intersection of the planes and the geometry of the ​“propeller” defines the perimeter of the load-bearing structure. To provide sufficient ventilation and reduce the self-weight of the structure, holes are cut out of the planes in a way that the remaining areas are connected and perform as a rigid and optimized composition. These connected planes consist of single beams and act as trusses. There are four, approximately 80-meter-long primary frames spanning from one end to the other. An additional six frames on either side stiffen the structure. The main and the secondary trusses are connected by perpendicular frames. If the trusses are covered, the air ventilates through the openings located in the primary and secondary frames. To avoid tilting or rotating around the tripod, the construction is stabilized by tension bars on both sides. These are placed within the area of the streets and therefore avoid introducing any loads to the historical buildings.