Bike was locked to outdoor office building bicycle racks. Office building is directly above Amtrak Union Station, and building bike racks are between Adams Union Station entrance and front of the office building. Racks are located away from both Adams sidewalk and Riverside Plaza foot traffic. Racks cannot be seen from sidewalks. I suspect an individual or group may semi-regularly target the area because after speaking with building management about the missing bike, they informed me that on occasion they have caught people at the bicycle racks with power tools.