They had a bird's-eye view of the entire Qu Shuang City below them. Qu Shuang City was built atop an immoral meridian. Immortal Qi filled the entire city, but immortal Qi was especially thin outside of the city. This caused the city to stand out from its surroundings. In particular, its shape.
The city was initially built in a haphazard manner - it did not take on any particular shape. If people wanted to reside in the city, all they had to do was apply with the City Lord for permission to build a house. As long as the City Lord gave his permission, they could build their house anywhere they wanted. That explained why there was so much space in the city.