Apart from the shaping of free-standing public and residential buildings in space, and the designing of large-scale urban units and complexes interpolation into an integrated block-type urban context has long been a prevailing theme of Belgrade's architectural design. In interpreting the demanding principles of this delicate discipline, which involves a defined relationship of the new structure with the visual and historical features of its immediate structural surroundings, designers usually combine standard and authorial solutions. Interpolations (incorporating, building into, inserting implanting) in Belgrade's architecture can be traced back to the 1870s, the period of the city's radical transformation from an oriental into a modern European city. Continuously encouraged by enterprising patrons and tolerated by insufficiently versed consumers, the practice of ostentatious insertion has continued into our days. At first developed through inserting multi-storey structures between the earlier lower ones, interpolation has become thematically extended to include spatially and plastically more comprehensive solutions, through accentuating the corner, positioning a new structure next to a single 'neighbor', expanding onto two or more streets (in case an entire block consisting of one or several rectangular buildings enclosing a courtyard is being interpolated), through interpolating upon interpolation (adding extra floors, mansard roofs, lofts, domes), various forms of 'sealing' larger locations etc. Over time interpolation has become adopted in industrial, landscape, memorial and religious architecture. Of the heretofore differentiated legitimate forms of architectural interpolation the methods usually used in Belgrade are contrastive insertion into a block authorial imposition onto a context and, more rarely, adaptive contextual approaches as well as few facsimiles or precise reconstruction's of demolished or dilapidated edifices. More responsible and cautious designers usually sought to find the least common denominator for all compositionally interrelated structures. In creating the relationships they took into account constituent elements of the existing buildings (volume, height, spatial organization, horizontal and vertical façade division, visual details symbolic emphases, construction, elements of materialization), but they just as much sought to establish dialogue and relations between the key elements of the interpolated structure and those of one of its two neighbors. It has been observed that the location of interpolations (street, crossroads, square etc) had an impact on the creation of relationships and that the growing complexity of a concrete situation led to more intricate solutions. Among recent interpolations in Belgrade's protected or central zones, occasionally reviewed in the Heritage, the multilevel office building at 23-25 Takovska Street, completed in 2008 after a 2003 design, stands out by its quality. It is a characteristic architectural design by a two-member team, Ksenija Bulatović (1967) and Vesna Cagić-Milošević (1970), the 2008 winners of a competition launched by the Novosti Company. This six-storey office building for rent is built on a steep, urbanistically delicate, high-traffic location in downtown Belgrade. By using a reduced cubic form and effectively superposed front planes receding in a stepped fashion towards the interior of the lot, and by laying emphasis on the extensive central volume with its glass curtain wall mirroring the surrounding buildings, the architects produced a recognizable and ostentatious neo-modern interpolation effected through a complex plastic procede. Striving for a structurality composed of several layers, treated in different ways heightwise and widthwise, they succeeded in establishing a geometric dynamism of the front façade. Their interpolation is neither modest, unobtrusive, nor strictly weaved into the context, because it does not contain echoes of Secession or academic eclectic architecture. In terms of type, it may be considered a moderate form of extrapolation or imposition of a new implant onto a context, which the authors do not even try to conceal. The structure has become a landmark and obvious dominant in the part of the street block occupied by its representative facade, but through certain historical evocations and non-canonical aesthetics it fits in the context of Belgrade's commercial architecture.