Always wanted to look into pre-Columbian cultures of Middle and South America. They've just re-opened a dig near Ayacucho in Peru.
Saw a piece on History Channel recently on lost civilizations. There's a site in southeast Turkey that doesn't belong to any known civilization, and it's thousands of years older than Stonehenge. It's a certainty that there were cultures of which we haven't found a trace--or if we did, we didn't know what it signified. They could have lived anywhere, reached any technological level, and then killed themselves off--the way we "modern" people tend to do.
One theory holds that the Black Sea was dry at one time. Something happened, possibly rising sea levels, and the people living there were inundated. The few survivors would pass down the widespread myth of the Deluge. There's a similar trope in Randall Garrett's Gandalara books.
There are carvings in the Sahara Desert that hint at a culture there before it became desert. Can anyone say for sure that all the deserts in the world are natural?
Yes, I shouldn't get archaeological theories from TV. I don't have time to go to the library or sift through all the BS on the Internet.
Other suggestions. Mongols as the good guys. Tibet? I've never heard of anything but Lost Horizon that even tried. The early Christian and proto-Christian sects who got weeded out by the early Roman church. There's a sect in Ethiopia that may have the real Ark of the Covenant.