Here is all the info I have found about Chicago using various A.I. search engines. Consider these rumors and not leaks.
Atmosphere and Environment
Old Chicago:
its depicted as a decayed, waterlogged urban landscape where the Great Lakes (specifically Lake Michigan) have been chemically and ecologically altered more than any other place on Earth.
featuring an ominous, horror-inspired tone with skyscrapers half-submerged in marshes and a labyrinthine sewer system.
The Seared Tower: The iconic Sears Tower (now the "SEARED Tower") remains a landmark, where a figure (Leon?) resides.
Locations & Gameplay
Adams and Wabash Station:
This specific underground station is a focal point where a mysterious entity has been attempting to communicate with Lodi.
The Department of External Observations (DEO): The headquarters of this Golden Age organization (where Lodi and Ikora Rey previously worked) is located here. It was a top-secret facility for studying anomalies and alien technology, including gravity-based weaponry like the Graviton Lance.
The Labyrinth: A series of tombs and crypts beneath the city streets where a "lost and maddened beast" (possibly an Aphelion) is said to hunt.
Narrative Significance
Binding the Nine: The primary objective in Chicago is to retrieve an "alien body" or essence hidden underground by the DEO to begin the process of binding the first member of The Nine to a physical form.
Factions: While the Hive are expected to be the primary threat, there are heavy hints of Taken or Scorn presence as the entity "Every nothing" seeks to infest the decaying planet.