Area 51 is a known military enclave. The actual base has long been a very closely-guarded secret, including wide "trespassers will be shot" stretches around the base itself and a large no-fly zone surrounding it.

According to conspiracy theorists, what we can see of Area 51 is just the tip of the paranoid iceberg. The base allegedly features elaborate underground labs, hidden tunnels, a dedicated extra-terrestrial runway that can disappear and reappear, and research programs dedicated to reverse-engineering alien technology.

In one particularly colorful and alluring detail, two different alleged former Area 51 employees reported working side-by-side with an alien being named "J-Rod" on cloning alien viruses and on a telepathic translator device (it's funnier if you imagine J-Rod as Jar-Jar; I'd watch that movie).

And the mystery of Area 51 is still only one example of the vast network of supposed government cover-up of alien contact. Pretty creepy stuff.