Tartaria was bui;t by and occupied by the Nephilim.
At a certain point they got unruly and destructive, as per the Book of Enoch, they all lined up for God's judgment and most of them were turned to stone, and buried in mud as with all of Tartaria. Some are buried with their heads sticking out of the ground, visable on Easter Island.
The nephilim that agreed to God's convenant, and still inhabit Earth are bound to keep away from humans and live amongst themselves. That's why it is important to stay away from Sasquatch/BigFoots.