Source: Into the Darklands, pg(s). 49
The urdefhan have eight major walled cities in Doga-Delloth, one of the vaults of Orv; Niovengia is the largest of them. It is the northernmost city on the vault's Sightless Sea coast, and stone piers extend out into the sea.
It is a city of towers and spires carved out of black basalt. There are glowing domes, as well as rookeries for the skaveling mounts used by the urdefhan. There are also numerous statues of the daemons worshipped by the urdefhan.