Deviant Art artist/contributor DirkLoechel of Germany has compiled a chart comparing the size of all the various space ships from science fiction. Wow. This is awesome. And you thought the Empire's battle cruiser was big? Just a spec of dust compared to some others. For more info and details please check directly at Deviant Art:
http://dirkloechel.deviantart.com/art/Size-Comparison-Science-Fiction-spaceships-398790051