Kareenburg, also called Kayburg, was the capital city on the planet Sergyar. It began as a large military cache dug into caverns where supplies in preparation for the invasion of Escobar were stored, then served as the location of a Prisoner of War camp for that war. From there it spread out and became the first city to be settled on the planet.
The terrain was semi-desert.
Located next to an active volcano, it suffered frequent earthquakes and was likely to experience an eruption within a few hundred years. Cordelia Vorkosigan chose to close her time as Regent for the planet by moving the capital to a better location, at Gridgrad.