Cloaked spaceship near Mercury. It's bigger than the planet and the planet is 1/10 the surface area of Earth so it can probably hold a crew the size of all the people in Europe. That's a lot of freakin' aliens.
So here's my theory, you have a big ass spaceship and you fly through space mining planets for metal which you then use to upgrade and enlarge your spaceship. After 100,000 years in space your spaceship is the size of Europe and you live happily ever after in space. Then one day you encounter a solar system with 8 planets and a dog named Pluto but the only habitable planet is taken so you park there and wait. However, it's conveniently getting warmer and warmer because it's fossil fuel loving inhabitants are doing global warming. When the Earthlings are gone because they can no longer live there you'll have a nice planet all your own that you can terraform back to health.
Only it doesn't go down that way. Instead the earthlings stop global warming which screws up the plan and so the aliens invade. At first the greedy Republicans help the invaders because of promises of wealth and power but then quickly get betrayed and have to suck it like everyone else. Massive wars between good and evil erupt just like at the end of days fulfilling the prophesies until Will Smith, played by president Obama, infiltrates the alien ship and uses their technology against them to save the world. Then we all live happily ever after. The beginning.