Originally, Li Si Te wanted to create a royal capital like Minas Tirith from "The Lord of the Rings", a castle integrated with the mountain.
It was that city integrated with the peak.
However, the Moon Slayer Sacred Mountain was not that unique mountain range; instead, it was two parallel ranges twisting through each other, forming a valley similar to an hourglass.
Right in the center of the valley was the entrance to the ruins.
If he pursued integration with the mountain city, it would be difficult to achieve symmetry, so he planned to construct a bridge-like support between the two peaks, incidentally enveloping the entrance to the ruins within the future royal palace. The royal palace could be a complex of buildings, founded on the summits of the two mountain ranges.
Ach wielded magic to reinforce the solidity of the mountains and arrange magic, ensuring the future royal palace was absolutely invulnerable.