Subway

The Subway is a train station that is located under Arkham City, in the Bowery.

Arkham Origins Incident
8 years earlier, the train station can be seen in the same location in Jezebel Center, but is closed.

Arkham City Incident
During his journey to find Mr. Freeze to make a cure for a deadly disease that most of Gotham, Joker, and himself are infected with, Batman needs to break into Penguin's headquarters, the Museum. But it is locked down and Batman is unable to hack his way in due to three communication jammers that are scattered around Arkham City.

After destroying the first two, he goes for the last one which is located in the underground train station, the Subway. After fighting five of Penguin's Henchmen, he destroys the final jammer and continues on his journey.

Trivia

 * There's a very old poster of Solomon Grundy on the walls of the Subway, along with a Vicki Vale Show commercial and a Santa Prisca tourism commercial.
 * There's a notable error with the Subway Station's location; when seen from the inside, the station has a round glass ceiling, and several buildings can be seen through it. However, its location on the map should be somewhere inside TYGER HQ (which has no buildings), and the glass dome is nowhere to be seen when seen from above.