Although it would take a day to travel from Horizon City of the Central Plains to the Central Plains City, the cities would not be connected to each other.
Moreover, there was no teleportation formation between Horizon City and the Central Plains City. Therefore, if Su Yi and Nie Ling wanted to travel to the Central Plains City, they had to pass through a mountain range.
The Chengguang mountain range was a dangerous place outside the Central Plains City. Although it was not as dangerous as the Demon Subduing Mountain, the Dark Abyss Cliff, or the Giant Lizard Island, there were still some demon beasts.
There was a mountain path in the Chengguang mountain range. The mountain path was extremely wide, and one could occasionally see the tracks of carriages passing by.