The Ruined City of Aerisport

Aerisport used to be one of the greatest ports of the Duchy of Urdus in the Toutus Empire. At its height, shortly before the Wars between the Empires, Aerisport had a population of 10,000. It sat on the River Rancor, and ships would swap cargo with river barges that would then travel up through prime farmland to Mesabridge and the Confederacy of the Ten Peaks.
During the Wars between the Empires, Aerisport escaped relatively unscathed. A raid by Telthyan pirates was fought off by the town guard.
This all changed with the Summoning. During his rampage across Kaelaross, Bhael created many Chaos Portals. One of these was in the heart of Aerisport, and it linked to the Chaotic Plane of Carceros (the reddish dot in the middle of the city map).
Further disaster occured when, during the fight between Bhael and the two lawful gods Rhondus and Adonar, the Godsblood Strait was created and the Godsblood Hills were heaved out of the sea immediately offshore from Aerisport. This shook Aerisport like an earthquake and six major fissures in the earth ripped open, swallowing buildings and a few remaining inhabitants (many had fled east when the Chaos Portal was opened). Other smaller splits in the earth are dotted around the city.
This left Aerisport landlocked and the River Rancor was diverted away from the stricken city.

These days Aerisport is abandoned by civilised humans. The map of the city does not show which buildings are ruined and which are still intact . About a third are ruined, either by the earthquake or monsters or even just time and erosion - it has been abandoned for 50 years.
The creatures of Carceros are more varied than the humanoid hordes of Hestoris, and are generally subterranean in nature. To start with they hid out in the surface ruins but then a clan of goblins emerged into Aerisport. These goblins, the Virrish-Guth, are master miners and excavators. On the plane of Carceros they expand and modify the vast dungeon networks. In Aerisport they have started in the fissures, digging sideways from the walls and sometimes creating safe pathways down into the fissures.
The other monsters appreciate the goblins' efforts - rather than killing and eating the goblins the other creatures have enslaved and bullied the goblins into creating underground lairs, usually connected to the fissures.

Nobody knows for how long or how far the goblins have excavated, but it is telling that the area that was the shoreline to the north-west of the city is being filled with what seems to be bucket- and barrow-loads of rubble, enough to form small hills. Some would say that underneath Aerisport is the biggest dungeon in Toutus, surpassing that underneath Seaview Keep.