The natural gate of the Tropic of Cancer sign tower of South Australia, "the natural gate", is located in the Tropic of Cancer square of Qing'ao Bay, Nan'ao County, Shantou City, is one of the 11 Tropic of Cancer sign towers built in China so far, at the intersection of the Tropic of Cancer and the eastern shore of China's mainland. On Nan'ao County, Guangdong's only island county, it is also the only Tropic of Cancer sign tower on the island. Every summer at noon, when the sun directly shoots the Tropic of Cancer, the sun will pass through the center of the ball above the "gate of nature", projecting the center of the platform to achieve the effect of "standless shadow".