The Northern Tropic (also known as the Tropic of Cancer) passes through 19 countries, so 19 small terraces are arranged on the stairs from the Binary Star Square to the West Gate, and on the terraces are the descriptions of countries and regions through which the Northern Tropic passes.
The stone pillars on both sides of the stairs are pillars with corresponding character descriptions of the twelve Chinese zodiac signs. The West Gate displays the four great inventions of ancient China, namely, papermaking, compass, gunpowder and typography. The Northern Tropic is a mysterious boundary between civilization and wilderness, where the lost ancient civilization has become an eternal mystery in history.
