For example: One-square wide walls that enclose nothing, like in the screenshot below:



Since I don't know the extents of stress large pics will put upon this forum, I'll only link to the higher-res version:

http://www.bfbeast.de/wp-content/jade_screen2.jpg

On one hand I like random stuff in towns, but those semi-finished walls inside the city are a blight to look upon. :)