The 'City at the Edge of Reality', Karonleas was built by Taramis and the Dunoln during the Third Age to facilitate travel between the Planes of Reshomme and, more importantly, to allow Taramis and Schiraman to leave Reshomme entirely and travel through the Wild Sea in search of the Hub Sphere.
Karonleas is the only significant structure on its Plane, which lies amongst the Fringes. The city is built around a series of concentric, circular walls - each higher than the last. At its centre lies the Heart of Karonleas, a great, blue, gemstone monolith that contains the souls of the city's population as well as controlling and animating its guardians and allowing travel to many other Planes.
The city is largely empty, abandoned by its people during the terrible upheavals of the Seventh Age who now wait, suspended within the Heart until the day comes when it is safe for them to live again.