While driving home from work I saw what I first thought was a blue pulsing police roof light; on second look I realized it was much too big to be on the roof of a car. The light was travelling at about 200 kilometers per hour and about 25 - 30 feet above the ground. The size of the light was round and approximately 30 feet in diameter and bright blue white pulsing light. After comparing what I saw with two other people I realized what I saw was something other than any ordinary vehicle.