I was being driven home and whilst looking out the window I noticed a large glowing object in the sky. At first I thought it was a plane or helicopter but when I realised the size of the object and how far away it was I realised that it could not have been a plane or helicopter. It was huge, with a dome shaped top and two box shaped parts on both sides. The dome seemed to fold inwards and light was emitted from the top into the sky from the inside of the dome. It was over 500ft in the sky and it would have been more than a mile away from me at the time, but the size of the object was massive. I forgot how long I was looking at it for and realized that over 20 minutes had passed. Then with it just disappeared, I can't remember how but it was gone and there was no trace of it in the sky