Cool! Actually many sources indicate it isn't completely impossible that the Balkan or Asia minor region had civilizations predating those of Egypt and Mesopotamia. However, until they've made C14 tests I think it's too early to say anything. As the structures are pyramids I'd say it's probably from before roman times, so 500 BC at the latest seems a reasonable guess IMO. But how old they could be at the maximum I won't try to guess. It'll be interesting to see what time they're dated to after C14 tests are made.
Bookmarks