819 Penn Avenue is aiming to provide a solution for downtown Pittsburgh monotonous commercial building complex and limited activity space for residents, which will break the traditional form of commercial buildings, and propose a new architecture structure system and passive design strategy. Following the design concept of The Behnisch Plan- "RIVERPARC" master plan, this proposal merges a wild range of ground facilities, so that public street and squares can communicate with each other, abandon the Functional singularity, maximize the social activities playground for neighbors. The lower part-culture and performing arts communication center and the middle part which is a considerable area of green space servings as one part of city public space. A free and flexible floor plan allows for the gathering of people from multiple fields as well as serendipitous meetings. The spiraling ramp not only works as the primary circulation path but also as an ambiguous transition space between interior and exterior. Users can access any floor with this slope, and its destination is the green space in the middle. The upper tower serves as office space, a diagonal atrium connected by small green space spared in each level, All floors are connected to the courtyard, terraces or roof garden so that every workspace is steps away from ample daylight and fresh air – natural ingredients for a creative workspace. By redefining three architecture typologies, the intimate of the lower part, the nature of the middle green space, and the efficiency of the upper tower, to create a new identity for the downtown Pittsburgh, transform it to be integrated into the public life of the city.