UFO Sighting in Chicago, Illinois on September 1st 1988 – Very big. Estimate 250-300 ft. 2-3 stories tall. Solid White Light.

This happened in Aug-Sept 1988 while at the Navy Recruit Base in Illinois. Our company was in the 2nd story of a 3 story barracks. I was in the back of the barracks around 2am on "watch duty". Very tired I lad down in a empty rack and closed my eyes. I was startled when I perceived light through my closed eyes and sat up quickly thinking I was busted by a company commander or someone had the barracks lights on. When I sat up though there were no lights on and everything was quiet. I slowly walked to the aisle way and looked and listened for anything. Nothing. I knew something was shining in my eyes so I walked the length of the barracks (maybe 150 ft)to the "front watchman". I asked him who came in to the barracks. He looked at me weird and responded no one.I told him I had seen a bright light and asked him where it came from. He said outside. I knew this was extremely bright like a flash light being directed in to my eyes and asked him what the heck was it. He replied that he wasn't sure. Maybe a car.... I dropped it and we talked for maybe 2 minutes when I began to walk back to my posted area. I took maybe 3 steps and the whole barracks lit up light it was day light outside. I stood there looking at everyone in their racks wondering how they are not waking up to this bright light. I turned to the other watch and said there is no way a car is doing this and headed toward the windows that ran the length of the barracks. The bottom panes were frosted so you couldn't see standing on the floor. We jumped up on top of the radiators that ran down the wall and looked out the clear panes. We were in the second to last barracks on the base. Just on the other side of the last barracks looked like an huge beam of light coming up on the far side of this last barracks. I try to explain it looking like a football stadium with light pouring out from the bright lights. After maybe 5-10 seconds of trying to analyze the light a long oval slowly appeared on the back side and steadily rose a couple stories above the 3 story barracks and then stopped and hovered in place. Super bright white light. I could not make out any details anywhere within this huge object. Just solid white end to end, top to bottom. I could feel reverberations, pulsating from the object. Almost like a generator but very deep in tone and fairly slow in frequency.I could feel the window pain vibrating and even feel it in my chest. As I watched this and took it all in I asked the other watch what he thought it could be. He responded he had no idea and asked what I thought it could be. I said UFO and all he could do was nod his head. I studied it in the 20-30 seconds it was there trying to take in every detail. Waiting for the next move when it just completely vanished. Like someone turned off a light switch. No more sound and no other light. Just gone. I was shaken from witnessing the event and my heart was racing. I knew I had just seen something unusual. We reported the event to the company commander the next morning and never heard anything about it again. We didnt get to investigate the other side of that barracks. We were in boot camp. I always wondered if the first time I saw the light if the object was actually descending. I went on to have a 7 year career in aviation. Electrician on the F-14 and never to this day have ever witnessed anything close to this that would even begin to explain that night.