Lake Canulus is a lake in the far east of Cyrodiil, between the Silverfish and Panther Rivers. (map)
Fort Cuptor is on the southern shore, and Abandoned Mine, Nayon Camp, and Lost Boy Cavern are all nearby. There are three Nirnroots around the lake, including one within the walls of Fort Cuptor. Leafrot Cave lies a little south of the lake.
If the Mehrunes' Razor official download is installed, the fort of Sundercliff Watch appears nearby. The last zone, Forgotten Tunnels, is accessible through a secret door beneath the lake.