Skavenblight

Skavenblight is the "capital city" of the Great Underground Empire. The best way to describe it is a giant pile of rats that explode (both the rats and the pile). It is located north of Estalia and north-east of Tilea, so basically where Andorra would be if it was in the Old World.

In more detail it's in the middle of a fetid swamp, while it is full of nasty swamp critters, dead skaven and plants which produce black rice like grain for the skaven to eat collected by barges which collect it.