A mysterious Tunnel Under Euphrates River.

The construction of a tunnel under the River Euphrates which linked secretly the existing royal palaces on either side of the river. It is believed that the tunnel was build between 2180 and 2160 BCE under the river Euphrates to connect the two halves of the city of Babylon in Mesopotamia.
The tunnel is quite long. It is said around 929 meters. Construction allegedly began with a temporary dam across the Euphrates, and proceeded using a "cut and cover" technique.
The tunnel allegedly spanned 12 feet high and 15 feet wide, it is presumed that it was used by pedestrians and horse driven chariots and connected a major temple with the royal palace on the other shore of the river, it was supposedly lined with brick and waterproofed with asphalt.
The use of abrasives to ease the task of cutting rock was apparently developed by the Egyptians at the time the pyramids were built. The Egyptologist Sir Flinders Petrie says the Egyptians cut granite and other hard stones using tubular drills and saws edged with corundum or other gritty substances.