The Watchtower is an orbiting satellite, and the true headquarters of the Justice League. League members are transported to the Watchtower from the Hall of Justice and the Cave. The Watchtower has sensors that can detect immense energy surges on the surface of the planet, but does not have any weapons systems.
When the Justice League decided to secretly establish an orbital base, they turned to the Green Lantern Corps for help. They gave the League a decommissioned Green Lantern base station that had been constructed from an asteroid. Hal Jordan and John Stewart towed it into Earth's orbit, and the station was modified to suit the League's needs, including the installation of Zeta-tubes. The League started operating out of the Watchtower after their base in Mount Justice was compromised. Its existence has been kept from public knowledge,with the aid of cloaking capabilities.
With the Light still in control of the Justice League, the Team had to infiltrate the satellite via another way. They used the Bio-Ship, and via a makeshift dock, entered. With the help of cure-tech, they negated the effects of the Starro-tech.
The Team celebrated the new year aboard the Watchtower and discussed the past events with the League.
In the Watchtower, John Stewart explained about Lobo and the Kroloteans. Adam Strange explained about Rann and showed a tech which traces Kroloteans. Nightwing decided that the Team went after the remaining Kroloteans and investigate on Rann.
Batgirl presented recordings of the walls of an ancient Bialyan temple to Doctor Fate, Zatanna, Robin and Nightwing. Fate translated the hieroglyphics, revealing an ancient ritual to cleanse a scarab.
Captain Atom hailed the Warworld to attempt negotiations, to no avail. Aquaman and Nightwing monitored from the Watchtower as Captain Atom joined other Leaguers in a frontal assault on the Warworld, while the Team infiltrated the vessel.
The Watchtower May 26, post-07:35EDT
After the Warworld launched a saturation missile attack, Aquaman used the Watchtower's systems to estimate the effectiveness of Earth militaries' defenses.
Nightwing congratulated the Team from the Watchtower after they succeeded in disabling the Warworld.
Following a successful mission, Nightwing officially handed command of the Team back to Aqualad. Shortly after, a boom tube opened, depositing the unconscious bodies of Leaguers who had been guarding the Warworld's key chamber.
Lucas Carr coordinated the twenty squads of heroes as they simultaneously attacked and disabled twenty MFDs. By the time all twenty MFDs were down, several heroes had returned to the Watchtower, including Kid Flash. When Blue Beetle reported detecting a twenty-first MFD at the North Magnetic Pole, and Flash and Impulse reported it to have already gone chrysalis, Kid Flash zeta-ed out to help.
In the mission room, several Leaguers watched G. Gordon Godfrey's report on Secretary Tseng's resignation and Godfrey's proposal of Lex Luthor as his successor. Captain Atom turned over the chairmanship of the League to Black Canary. Nightwing informed Aqualad of his decision to take a leave of absence from the Team.
In the memorial garden, Tigress and Kid Flash discussed their new identities, Robin and Wonder Girl welcomed Static to the Team, and Miss Martian and Superboy talked about Tim and Cassie's new relationship. The discussions were interrupted when Aqualad summoned everyone to the mission room.
Batman informed the assembled Team that they would now operate out of the Watchtower alongside the League. The Leaguers left them to carry on, and Aqualad handed out mission assignments.
Background in other media
The first JLA base to use the name "Watchtower" was built on the moon's surface during the Grant Morrison run of the JLA series. Earlier bases in Earth's orbit were called the Justice League Satellite; they returned to a satellite after Infinite Crisis.
This marks the fifth animated appearance of the Watchtower. It appeared in the DCAU, there were two: one in Justice League (which was destroyed in the finale) and a new model in Justice League Unlimited. It also appeared in The Batman, Justice League: Crisis on Two Earths and Batman: The Brave and the Bold