The "Nature Gate" is the Tropic of Cancer sign tower in South Australia. It is located on the Tropic of Cancer square on the island of Nan'ao, Shantou City. It is 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".