These aliens might also be closer to home than you might think and, have been here for far longer than
one might imagine! Through history many civilizations spoke of how their ancestors came from within the earth.
Some indian tribes also speak of this same scenario! Here is a segment that I found in an article I found!
You can read the rest
HEREBourke Lee, in his book 'DEATH VALLEY MEN' (MacMillan Co.,N.Y. 1932), chapter: "Old Gold", describes a conversation which he had several years ago with a small group of Death valley residents. The conversation had eventually turned to the subject of Paihute Indian legends. At one point two of the men, Jack and Bill, described their experience with an 'underground city' which they claimed to have discovered after one of them had fallen through the bottom of an old mine shaft near Wingate Pass. They found themselves in a natural underground cavern which they claimed to have followed about 20 miles north into the heart of the Panamint Mountains. To their amazement, they allegedly found themselves in an huge, ancient, underground cavern city. They claimed that they discovered within the city several perfectly preserved 'mummies', which wore thick arm bands, wielded gold spears, etc. The city had apparently been abandoned for ages, except for the mummies, and the entire underground system looked very ancient. It was formerly lit, they found out by accident, by an ingenious system of lights fed by subterranean gases. They claimed to have seen a large, polished "round table" which looked as if it may have been part of an ancient council chamber, giant statues of solid gold, stone vaults and "drawers" full of gold bars and gemstones of all kinds, heavy stone "wheelbarrows" which were perfectly balanced and scientifically-constructed so that a child could use them, huge stone doors which were almost perfectly balanced by counter-weights, and other incredible sights.