The Canyon of the Three Gates is the only way in and out of the crater of Osrakum. It is a narrow defile running between sheer, cliff walls. Three fortresses have been built along its length, the three 'gates': the Green, the Red or Blood or Ichorian and the Black or Death Gates. A channel cut anciently in the floor of the Canyon allows excess water to be carried out of the lake that fills the crater of Osrakum.

The diagram shows only the portion of the Canyon which lies between the Green and Black Gates and is not drawn to scale.

The Red Caves lie between the Ichorian Gate and the Black Gate.