Probably an engineer. After all, architects design buildings but, usually, they have nothing to do with the calculations and construction methods employed to build their design.
"Engineer" is a very generic term for a wide variety of fields. An architect is actually a specific type of engineer who not only designs buildings but also plans their construction. This requires intimate knowledge of the materials used; e.g. how long they will last, the forces they can withstand, etc., and you can bet there is a great deal of geometric calculations involved. You are mistaken if you believe an architect is simply a fancy term for "graphic design artist for buildings". Architects don't simply put onto paper whatever comes to mind without a care for practicality. After all, if it can't be built, you'd be out of a job very quickly.
