Location
From Arkham Horror Wiki
The Arkham City game board is divided into several locations, which represent parts of the city. Locations are where much of the game action happens, as investigators move around and have encounters.
Each location belongs to a neighborhood next to thematically related locations. All of these areas are connected by streets.
Each location is marked with icons depicting the most common type of encounters at that location. Some locations, such as Arkham Asylum, have special icons denoting a guaranteed method of acquiring an item (for example, at Arkham Asylum investigators can recover their Sanity).
Some cards use the term "location" loosely. It may mean your current location which can include street areas and Other Worlds. See specific card descriptions for any clarifications.
Locations also have a stability rating indicated by a green or red diamond: green locations are stable, and monsters and gates will not appear there automatically; red locations are unstable, and monsters or gates can appear in these locations as a result of an encounter or drawing certain cards. Unstable locations, while more risky, also give players the possibility of encountering an Ally, and Clue tokens often appear in unstable locations when Mythos cards are resolved.
During the Arkham Encounters phase any investigator in a location with no gate can draw a location card from the deck for that neighborhood and follow the instructions. They can also choose to undertake the location's special encounter instead of drawing a location card.

