One of the most awesome things I ever saw was an entire space ship -drop pods included- with everything you need, even prisoner containment cells.It also had an armory of course for weapons and there was a smaller ship next to it with banshees and shade turrets.
Another thing was an entire race track that went all the way around forge world. This map is called GTA. Although in GTA, you have to keep the warthog you driving at full speed at all times other wise you would fall into the water.