From Tolkien Gateway:

''Morgul Vale (Imlad Morgul in Sindarin), was the valley of the Morgulduin in the western Mountains of Shadow. At its outflow into Ithilien stood the fortress of Minas Morgul ("Tower of Dark Sorcery"). The name was only used in the later Third Age, after the Nazgûl captured the fortress of Minas Ithil and turned it into the Tower of Dark Sorcery. The only vegetation in the valley was to be found along the river - fields of white flowers believed to give off noxious vapors.''

To clarify, it borders the following regions:

• Minas Morgul
• The Crossroads