Quests starting in The Tower of Orthanc

NameLevelZoneArea
Instance: In The Presence of Saruman 72 Isengard The Tower of Orthanc 

Quests involving The Tower of Orthanc

NameLevelZoneArea
Instance: The Wizard's Vale 72 Isengard Isengard 
Isengard: The Tower of Orthanc 75 Middle-earth Global