The Lost and Found City of Egypt

An ancient city at the mouth of a mighty river was the recipient of untold wealth due to the shipping trade, but changing conditions along the coastline left it sunken under water. This is the story of the lost Egyptian city of Thonis, also called Heracleion. Once thought to be a myth, it was found exactly where it always was, except underwater in the Mediterranean Sea. Heracleion's ruins are filled with expensive artifacts, leading experts to believe the disappearance of the city was relatively sudden, or else those treasures would have been moved. The upshot is that you can build flimsy structures or sturdy stone structures, but if your foundation is on the coastline, you're at the mercy of the sea. The term "filthy secrets" in the video title is just marketing. (via Digg)