Tower

"I thought since Luthor Corp now owns the D.E.O., National City could use its own collective. A headquarters to keep this city safe, to work outside of corporate and government oversight, whose interests might not always side with justice. [...] A place for my Superfriends to work, whenever they should need it."

- J'onn J'onzz explaining the Tower to Kara, Alex and Winn

The Tower is the headquarters of the Superfriends.

History
Taking inspiration from the S.T.A.R. Labs hall established as a headquarters by Barry Allen, J'onn J'onzz repurposed a section of his building to act as a secret headquarters outside of governmental oversight, for the Superfriends. When they dropped by his office, J'onn showed them the base and explained his decisions.