7. Flying Ninja Fortress http://brickset.com/sets/6093-1/Flying-Ninja-Fortress The only official Lego set on our list, the Flying Ninja Fortress was released as part of the Lego Ninja line in 1998. It featured wall segments that could be detached and rearranged, which almost begged you to buy two and combine them together! It contained 654 pieces and nine minifigures - brickset.com