Seven small hills, with Tianshu and Tianxuan being the highest, followed by Yu Heng Hill.
Generally speaking, unless there is a Spirit Vein hidden, the higher the hill, the more abundant the Spiritual Energy.
This is best proven by Qin Mountain.
Qin Mountain is the tallest near Purple Cloud City, and due to its sparse population, the Spiritual Energy at the summit is also the most abundant.
Apart from Qin Mountain, the hills and valleys where Qingtian Academy is located also have much more Spiritual Energy than Purple Cloud City, which is presumably why Qingtian Academy was built here.
Xin Lin, who has now reached the Beginner phase of Gathering Spirit, is quite sensitive to Spiritual Energy and can see at a glance that among the seven hills, Tianshu Hill, Tianxuan Hill, and Yu Heng Hill have the best geographical locations and are also more abundant in Spiritual Energy.
