The Niben River (known to the Khajiit as the River Malapi, sometimes called the Imperial Run) is a large river in Cyrodiil. Its source is Lake Rumare in the Heartlands and it empties into the Topal Bay. It is divided into three sections:
The Red Ring Road crosses over it near Lake Rumare, over a rather impressive bridge (second only to the Talos Bridge in size). Fort Alessia and Fort Variela border the Niben on the west, while Shinbone Cave and the Ayleid ruin Culotte border it on the east side. A Wayshrine of Talos can be found near Fort Variela.
It lies across the Niben River, splitting it into two parts, upper and lower, and so is technically a lake rather than a bay, which means that the Khajiit name for the bay, Lake Makapi, is more accurate. In addition, the Larsius River, the Corbolo River, the Silverfish River, and the Panther River all empty into Niben Bay.
In 3E 433 a floating island appeared in the bay, on which a door to the Shivering Isles was opened by Sheogorath in his search for a champion. From the east side of the bay going south and around, Fort Aurus, Fort Irony, the Ayleid ruin Bawn, Flooded Mine, a Wayshrine of Zenithar, and Veyond Cave all border the bay. Fort Grief Island sits near the mouth of the Silverfish River, while the underwater section of Fathis Aren's Tower can be found far south of the fort.
It is a very abundant source of Nirnroot. Leyawiin completely blocks the river, so it must be assumed that the water flows underground or through the sewers, because otherwise the city would act as a dam, and be completely flooded.
Water's Edge sits on its northwestern shore, with Rockmilk Cave a short distance to the north, and the Ayleid ruin Telepe and Undertow Cavern further south of Water's Edge. Fort Redman, Fisherman's Rock, and Amelion Tomb all sit on the eastern shores.