In addition to his capital, Rîm-Sin had inherited from his brother the control of the southern group of cities, Ur, Erech, Girsu and Lagash, all of which lay to the east of Larsa and nearer to the coast; and it was probably before his conquest of Nîsin that he took Erech from Damiḳ-ilishu, who had been attacked there by Hammurabi two years before. For in more than one of his inscriptions Rîm-Sin refers to the time when Anu, Enlil and Enki, the great gods, had given the fair city of Erech into his hands.[86] We also know that he took Kisurra, rebuilt the wall of Zabilum, and extended his authority over Kesh, whose goddess Ninmakh, he relates, gave him the kingship over the whole country.[87] The most notable result of his conquest of Nîsin was the possession of Nippur, which now passed to him and regularized his earlier claim to the rule of Sumer and Akkad. Thereafter he describes himself as the exalted Prince of Nippur, or as the shepherd of the whole land of Nippur; and we possess an interesting confirmation of his recognition there in a clay cone inscribed with a dedication for the prolongation of his life by a private citizen, a certain Ninib-gamil.[88]
That Rîm-Sin's rule in Sumer was attended by great prosperity throughout the country as a whole, is attested by the numerous commercial documents which have been recovered both at Nippur and Larsa and are dated in the era of his capture of Nîsin. There is also evidence that he devoted himself to improving the system of irrigation and of transport by water. He canalized a section in the lower course of the Euphrates, and dug the Tigris to the sea, no doubt removing from its main channel an accumulation of silt, which not only hindered traffic but increased the danger of flood and the growth of the swamp-area. He also cut the Mashtabba Canal, and others at Nippur and on the Khabilu river.[89] It would seem that, in spite of his Elamite extraction and the intimate relations he continued to maintain with his father Kudur-Mabuk, he completely identified himself with the country of his adoption; for in the course of his long life he married twice, and both his wives, to judge from their fathers' names, were of Semitic descent.[90]