I was on the roof of a building, looking straight up at the stars at roughly 11:00 PM. Suddenly just above the Northern Horizon, movement caught my eye. I turned my attention to right above the Horizon, as I watched an Illuminated Sky-Blue Solid Colored Disc move from the Northern Horizon to the Southern Horizon in about 10 seconds, fading away as it approached the Southern Horizon. It appeared to be about the size of a frisbee, if one were to hold a frisbee at arms length away from ones' face. It seemed like it may have been traveling in the upper atmosphere, in which case it would have been rather large. It made no noise, just the lighted solid sky-blue color over the entire disc.