The paper argues the role of interior spaces in linking the urban open space configuration. The interior space is discussed as extensions of urban spaces and urban spaces as extensions of interiors with specific reference to a case study selected in Balıkesir urban fabric. Under the light shed by these discussions, the paper questions the certainty of boundries between exterior and interior, thus between interior design and architecture. While the first axis of discussion focuses on the duality between interior and exterior, the second axis of discussion concentrates on the insertion of new and contemporary architectural and spatial features into an existing and historic context. The Museum and Library of Photography project in Balıkesir, which is selected as case study, is based on a VOID connecting what exists with what disappeared long ago in a totally new combination. Consequently, paper shows that architectural identity of the existing (and sometimes disappeared) heritage is reproduced via injection of this new hybrid (interior-exterior) into the very heart of the existing urban fabric. The hybrid design of the VOID intends to resolve the tensions between the contrasting features of restoration and intervention merely by understanding the conditions and fundementals of the process of historical layering in the town.