[@Rabidporcupine]
The tower and its city are situated in the middle of the continent, so you'll probably pass it on your way to other neighboring countries. The fortress city was primarily intended to protect the tower, but it has since become an important trade hub. It's also fairly close to the Zodiac territories, so if Chatak wanted to make a trade agreement with the humans, the Sealed Tower City would be a good place to go.

There's also the fact that the tower is ridiculously, absurdly tall and would probably be visible for thousands of miles.