Photograph of the McCormick Tribune Campus Center, Illinois Institute of Technology, showing the Exelon tube and the Green Line tracks from below. The concrete and stainless steel tube encloses a 530-foot stretch of the Chicago Transit Authority's elevated Green Line commuter rail ("L") tracks.... Show morePhotograph of the McCormick Tribune Campus Center, Illinois Institute of Technology, showing the Exelon tube and the Green Line tracks from below. The concrete and stainless steel tube encloses a 530-foot stretch of the Chicago Transit Authority's elevated Green Line commuter rail ("L") tracks. Photograph made available via Illinois Tech's institutional repository with the permission of Richard Barnes. Show less