Shipyard

The shipyard was a building located on the southeastern part of the perimeter wall of Arkham City, in the Industrial District.

Description
This area was likely used to deliver and receive goods through overseas and perhaps also used as a storage facility for the TYGER guards.

Batman: Arkham City
In the main game, the building was inaccessible, but a Riddler Trophy is located at the main entrance and part of the building can be seen in the back of the Sionis Steel Mill.

In Harley Quinn's Revenge, the building plays a prominent role and serves as the main setting for the DLC.

Weeks after the incident, Harley Quinn returned to Arkham City and set up her own gang after The Joker's death. She retook the Industrial District and the Steel Mill, while also setting up base in the abandoned TYGER shipyard. She continues to conduct business from there, while also trying to cope with the Joker's demise.

Batman arrives in the area after hearing of Harley Quinn kidnapping hostages. He attempts to save them, but is shot after trying to save one from getting killed by Harley herself, rendering him unconscious. The henchmen drag his unconscious body away to be put in a Joker Monument in his shrine, where he is put in a meditating state and locked in an airtight plastic ball.

Two days later, Robin is sent by Oracle to investigate Batman's disappearance as communication was lost when he was captured. Robin infiltrates the shipyard and looks around for clues to Batman's disappearance. Eventually, after navigating through the building and defeating henchmen along the way, he enters the same warehouse where Batman was captured to find his utility belt. He continues to follow his trail soon after. He then enters the Joker Shrine to find Batman trapped in the monument. After realizing that he is running out of air in the bubble, he needs to retrieve the keycard that operates the monument from Harley herself. After subduing her, he returns to free Batman, but is forced to battle against a large group of henchmen, including a TITAN infected henchman. After surviving the fight, he frees Batman, who regains consciousness. After returning his belt, Harley gets on the loudspeaker and warns them that she is going to blow the place up after showing a bomb. Batman demands Robin to save the police while he will defuse the bombs. After disarming the single bomb and learning that it is the same as the explosives stolen last week from the GCPD Lockup, he calibrates his cowl to track the explosives. After finding and defusing all of the bombs, Harley tells him to come find her. Batman heads back to the Joker Shrine, where he finds her with a detonator and several Wonder City Mechanical Guardians, which she somehow got a hold of. After defeating the robots, Batman subdues her and attempts to take the detonator and defuse the bombs, but unfortunately, the bombs were rigged to blow and that defusing them is not possible. Meanwhile, Commisioner James Gordon runs towards the side of the building, only to be blown back by the explosion, but surviving. As he believes that Batman perished in the explosion, he and Harley dive out of a window, escaping the inferno. But after the escape, Batman asks Gordon for Robin's location, but Gordon replies by saying that he thought he was with him. Batman then looks at the building and believes that Robin perished in the explosion. Angered by this, Batman asks what Harley has done, which she replies by saying that now, he knows how it feels to lose a loved one. As he continues to look at the burning building in despair, Harley takes out a hidden blade and attempts to stab and kill Batman once and for all, but before she could kill him, Harley is suddenly hit and knocked out by a Shuriken and it reveals that Robin survived and the GCPD officers are safe. Secretly relieved, he says that he is done here and grapples upwards.