Prolgu was the capital and only city of the Ulgo people. The name "Prolgu" referred to both the ruined and abandoned ancient city, as well as the extensive cave network beneath which housed the Ulgo people after the Monsters turned mad. It is located in the central mountain range of the western continent.
Prolgu rivalled Kell as one of the most holy places in the world. The Ulgo tribe of prehistory were one of the races of men called the 'Godless Ones' - which included the Morindim and Dals amongst others. One of their number, a man called Gorim, was successful in beseeching the father of the Gods - UL - to be their deity. As such, UL christened the tribe the Ulgos, made the Gorim their leader, and extended his protection around the city of Prolgu, at the summit of a mountain.
UL was also the totemic God of the creatures created by his descendant deities - the Algroths, the Eldrak, the Dragon and others. These creatures were driven mad by Torak's cracking of the world during the War of the Gods and rampaged through Prolgu. UL led the Ulgos beneath the city to the safety of the caves, where they have since dwelled in his protection.
Ce'Nedra remained there whilst Belgarath took the Orb back from Ctuchik, as she was the most vulnerable to attack at that point, and the only safe place was Prolgu.
Errand was also renamed by UL as his proper name, Eriond, at the beginning of the King of the Murgos.