The apartment of a young businessman is located within a residential-business complex of a relatively recent, ambitiously designed infill building in Zagreb’s Lower Town. A unique and privileged location next to the central city square provoked the developer to maximize the interior residential and business standards within the building in terms of the architectural expression, technological equipment and building maintenance if compared with the standard Croatian practice. Within such a framework, a young future resident purchased two adjacent residential units during the building shell construction stage with the intention of connecting the two units into an integral space with more luxurious proportions. The fortunate circumstance of this intervention was that the original design allowed the possibility of a relatively easy connection by demolishing a section of the wall filled with bricks within the reinforced concrete load-bearing wall. The two apartments were thus simply connected into a single space. The inverse design approach from the usual and routine practice, (where the existing floor plan is filled with an as large as possible programme) is here replaced by the freedom to formulate a simple design programme in just under 200 m2. This also required additional responsibility, since there is no place for justification of mistakes in this, for architects, rare and lucrative situation. The spatial organization of the load-bearing existing structure of connected residential units has largely defined the functional scheme.