The Metro Tower was a building, located in Metropolis, adopted by the Justice League following the Cadmus incidents.
The Metro Tower was originally intended to replace the second Watchtower as the League's headquarters, thus bringing the League literally as well as figuratively "down to Earth". The Watchtower continued to be used in conjunction with the Metro Tower for at least the next fifty years, though by that time a newer and much larger tower stood in its place. Aswell as a second base for the league, the tower was meant to be an embassy for the league to be "closer" to the people of earth because following the events of the cadmus crisis. After the Cadmus crisis the people of earths did not have any trust in the league because of luthor framing the league for the firing of the miliatary weapon in the second watchtower. The metro tower was superman's idea originally.