Here is a conceptual design that I recently completed for one of my clients... this is hand drawn and then colored with ad markers.  This is a rooftop over a 5 story studio apartment building in LA.   The challenge here was transforming the spaces predetermined by the building architect into exciting, usable, unique areas through creative site-programming.  The two white areas in the center represent large gaps in the structure.  At the base of each gap is a courtyard garden - drawn below.