A simplified and user-friendly reusable modular building block system, for use by the professional architect or home design enthusiast, allowing for the creation of custom architectural scale models of building designs similar in appearance and function to professional scale models produced in architects' offices is presented. The building block system pieces are comprised of interlocking injection-molded solid plastic parts and grouped in five classes of various corresponding shapes and sizes. The construction and grouping of the block system pieces can be connected together at the user's discretion in a limitless variety of creative configurations, thereby forming the walls, floors, ceilings, roofs, door and window openings, and other building design elements of an architectural model at 1:48 scale (1/4''=1'-0'') based on the user's unique house design, or an existing design if so desired.