• freat rift valley,
• vreat rift valley,
• breat rift valley,
• hreat rift valley,
• yreat rift valley,
• treat rift valley,
• geeat rift valley,
• gdeat rift valley,
• gfeat rift valley,
• gteat rift valley,
• g5eat rift valley,
• g4eat rift valley,
• grwat rift valley,
• grsat rift valley,
• grdat rift valley,
• grrat rift valley,
• gr4at rift valley,
• gr3at rift valley,
• grezt rift valley,
• grest rift valley

The adjective form of "Great Rift Valley" is "Great Rift Valleyic" or "Great Rift Valleyian".