Nightingale Hall is a location in The Elder Scrolls V: Skyrim found in The Rift
This is the base of initiation for all members of the Nightingales. These are the mortal agents of the Daedric Prince: Nocturnal. They protect the Twilight Sepulcher from intrusion and act on the will of Nocturnal.
It is here you can acquire the Nightingale Armor Set.