A retrofit trampoline into a gazebo, covered shelter, or the like is created by attaching upward-oriented and/or sideways oriented poles to existing vertical poles of a trampoline. A removable cap is attached to the top of the vertical poles onto which the upward-oriented and/or sideways oriented poles can attach. The sideways oriented polls can be a rollable fabric which can be unrolled to form sidewalls. The upward-oriented poles can meet and/or cross at a horizontal center of the trampoline and/or support a canopy cover which is solid and/or mesh. Seats, such as circumferential seats, which extend around the perimeter of the trampoline inside of the side walls can be added. In some embodiments, a tensioning rope attaches the removable cap to a lower section of the trampoline or ground for support and in some embodiments a tensioning rope is used to hold the cap to the vertical poles.