[![City with little urban sprawl](https://i.stack.imgur.com/amBDa.jpg)](https://i.stack.imgur.com/amBDa.jpg)

I am making an RPG and am using this image (source: <https://www.pixiv.net/en/artworks/58916801>) as inspiration for a large city. 

This city:

* Is located in a country roughly the size of Panama
* Has some flat land to expand onto near it
* Stops abruptly and descends into wilderness
* Is entirely covered in skyscrapers up until its end

Why would a city be entirely comprised of skyscrapers but stop abruptly without suburbs? I know that the city could not expand into the waterfall, but there appears to be some flat land near it that it can expand to (in the background). That land is not used, not even for agriculture. How could this happen? Are there any real life examples of cities like this? 

Assuming that the city is inhabited by humans and has the same physics and geology as Earth (ignore the mountains in the background). 

To confirm: The planet is at a present day tech level. Computers, airplanes, and cell phones are commonplace throughout the world.