This massive robot/spaceship was built by an advanced alien race and is 4 times as big as earth. It serves as a home for their people and the interior is all livable. There is a large clear dome atop the ship that they grow plants in. The photosynthesis of the plants produces energy for the ship, so they fly near suns to let the plants refuel it. The ship has 4 drill legs attached to it that allow it to anchor itself on planets in case they find one that looks inhabitable or is rich in resources.