The design of a rooftop open-air swimming pool in China typically involves considerations for structural integrity, waterproofing, safety, and aesthetics. These pools are often built with reinforced concrete and special waterproofing membranes to ensure they can withstand the weight of the pool water and prevent leaks. Safety features like secure railings and non-slip surfaces are also crucial. Aesthetically, the design may incorporate traditional Chinese architectural elements or modern designs to blend with the building's overall look.