Underground Equalist facility

The underground Equalist facility is a large structure located deep within the tunnels beneath Republic City.

History
After Tarrlok told Tenzin that the Equalists had ambushed himself and Korra at City Hall, Tenzin spent much of his time on the phone, hoping to gather information on where Korra could have been taken. During this time, Lin Beifong, who was in the hospital, heard via radio that the Equalists had captured Korra, and immediately rushed to the Police headquarters. Upon her arrival, Lin broke Mako, Bolin, and Asami out of their cells, and took them to see Tenzin at City Hall. Once the group arrived at City Hall, they encouraged Tenzin to search for the Avatar with them, to which he agreed.

With no leads to go on, the group had to rely on pure speculation in their hopes to find Korra. Lin Beifong made the remark that the Equalists had probably taken Korra somewhere underground. Bolin remarked that this theory made sense, as he believed that he was taken through an underground tunnel while he was an Equalist prisoner. The group used Oogi to travel to the location where Bolin had been kidnapped, and followed the trail that Mako, Korra, and Naga took during their attempt to rescue Bolin. Lin used her seismic sense to survey the area, and located a tunnel nearby, to which Bolin remarked that the location "smelled familiar". Upon finding motorcycle tracks leading into the underground tunnel, Lin proceeded to open the tunnel's entrance by using her metalbending, and the group proceeded inside.

While traveling through the tunnels, the group hid from two Equalists on motorcycles that opened a secret passage. Once the Equalists were gone, Lin used her metalbending to unlock the lock behind the door, and the group entered the secret passage. Eventually, the group came to a large facility that utilized metal trams to transport goods and people to other Equalist locations. The group overheard an Equalists mention that one specific tram goes to "the prison", and Tenzin assumes that that must be where Korra is being held. The group sneaks onto the tram and travels down the tunnel. Upon reaching their destination, Lin uses her metal cables to subdue two Equalist guards, and the group enters the prison facility.

Lin proceeds to use her seismic sense to get a complete view of the facility, and remarks that while she doesn't see Korra in the prison, the captured metalbending police officers are in a cell in the prison. Bolin and Asami stay behind to watch the two subdued guards while Tenzin, Lin, and Mako proceed down the prison's corridors. At one corner, the group runs into two more Equalists, who are quickly overpowered by a strong blast of airbending by Tenzin. Mako runs up to one of the guards and demands him to tell them where Korra is. Meanwhile, Lin finds the cell where her officers are being held, and she realizes that Amon has already removed their bending.

After leading her officers back to Tenzin and Mako, who is still interrogating an Equalist guard, the guard tells them that the Equalists don't have Korra, and that they didn't attack City Hall. Tenzin then realizes that the entire thing was a lie devised by Tarrlok, and that he must have Korra. The prison's alarm then proceeds to go off, and Tenzin, Lin, Mako, and the rescued officers rush back to the tram, where Bolin and Asami are waiting for them. As they attempt to escape on the tram, another tram, filled with Equalists, begins pursuing them. Bolin then earthbends part of the tunnel's walls in front of the tram, preventing them from being able to follow. At the other end of the track, however, the Lieutenant, mecha tanks, and numerous other Equalists are waiting for them. Realizing that they still have company, Lin metalbends part of the tram's overhead railing down, causing the tram to fly upward, into a tunnel that Lin quickly creates with her earthbending. She then earthbends a hole in the facility's ceiling, and the group escapes.