The answer is, amazing discoveries are made all the time! Just this week there are news reports that a new, unheard of ancient Sumerian city has been discovered in southern Iraq.
http://www.stumbleupon.com/su/1WrVAB/www.suite101.com/content/a-new-sumerian-city-has-been-discovered-in-southern-iraq-a230390
The ruins are located south of the Sumerian city of Eridu. Isn't it amazing that with the endless warfare in Iraq over the past few decades, the invasions and retreats involving hundreds of thousands of troops, and chaos and looting of ancient ruins, this new discovery has been made. Presumably in the years ahead, work on these ruins will help shed more light on the civilization of Sumer and Akkad some 4,000 years ago.
My fantasy novel, Gettysburg Passage, from Amazon, uses a similar plot devise to drive the fast-paced action of the narrative. Mixed together are: 1) a mysterious, powerful, newly discovered ancient artifact; 2) a strange burning cave portal found near the Gettysburg American Civil War battlefield; 3) odd, real-live sightings of long-dead famous warriors; and 4) through mystics and dreams, an appeal for help from a lost civilization from the ancient past (Sumer, Babylon, Greece, Egypt? I am not saying!).
Read the reviews and check out a free, sample chapter. http://www.amazon.com/Gettysburg-Passage-ebook/dp/B00408AOMW
Gettysburg Passage, only $2.99 from Amazon.