The most distinctive feature of the SWFC's design is the trapezoid aperture at the peak. The original design specified a circular aperture, 46 m (151 ft) in diameter, to reduce the stresses of wind pressure[16] and to reference the Chinese mythological depiction of the sky as a circle.[16] It also resembled a Chinese moon gate due to its circular form in Chinese architecture. However, this initial design began facing protests from some Chinese, including the mayor of Shanghai, Chen Liangyu, who considered it too similar to the rising sun design of the Japanese flag. Pedersen then suggested that a bridge be placed at the bottom of the aperture to make it less circular.[3] On 18 October 2005, KPF submitted an alternative design to Mori Building and a trapezoidal hole replaced the circle at the top of the tower, which in addition to changing the controversial design, would also be cheaper and easier to implement, according to the architects.[3][17] Foreigners and Chinese alike informally refer to the building as "the bottle opener".[18] Metal replicas of the building that function as actual bottle openers are sold in the tower's gift shop.
