Respect to the first regulation of the place and situation established by the initial development of Plzeňská is important for the selected design of masses on then one hand. Working with the phenomenon of the green slope at whose foot the site is located together with continuing with volumes of the new development around the bridge connecting the Mrázovka and the Strahovský tunnels matters no less. We have been working with the principle of cutting the slope in three irregularly broken strips of mass; the two end blocks are extruded from the site while the middle one ´is preserved´ in the form of a green slope transpiercing the new building. This way interesting relations are established between both ´legs´ we have created to divide the building and let daylight in. Structuring and hierarchization of surfaces of this puzzle work with differentiation of vertical envelopes of both wings, horizontal cutting surfaces of the roof or the base, and the outer skin in the form of a fully glazed double facade also used as a roof to the atrium. An important element linking our project to the vicinity is the design of the streetscape. We consistently cling to the concept of interpreting the formed masses as worked parts of the original green slope that continue in the space above the tunnel′s portal and the adjacent park Sacre Coeur. That is why we work with an extensive green roof that may from place to place contain an intensive green island linked for example to the entries to the terraces on the top stories. The design of these roofs is crucial for the building in this particular case – due to the position on the bottom of the valley – the roof is, in fact, its fifth facade. On the south and east sides, i.e. towards the biggest source of noise and pollution by emissions and also towards the direction from where flows in the highest solar load, an outer layer of a curtain wall is added to the internal envelope. This additional ventilated layer crucially affects the building′s thermal balance and provides natural ventilation and effective shading in the offices and, at the same time, does not block valuable views to the city – something other facades than curtain walls can hardly grant. The curtain wall also roofs the atrium, yet it transforms in a thermally insulating single-ply facade here. Prime exposed roof areas are composed as green also because by its position in the slope the building offers enough less valued areas for technology usually placed on roofs of office buildings.