It is a conical shaped structure built of boulders, roughly 230 feet in diameter, 30 feet high and weighing an estimated  60,000-tons, 40 feet underwater in the Sea of Galilee.  And archaeologists have no idea what it is.   Based on the build up of sediment, it is between 2,000 and 12,000 years old, which is too wide a range to help identify it.  It’s not even clear if the structure was built on land when the sea levels were lower, or if it was constructed underwater.  The structure was located in 2003 by sonar scan. Now ten years later, researchers from the Israel Antiquities Authority are mounted an expedition to attempt to learn more about the unexpected mound of boulders, which they speculate could have been a burial site, a place of worship or even a fish nursery.

Structure at bottom of Sea of Galilee could reveal secrets of ancient life in Middle East

Archaeologists said the only way they can properly assess the structure is through an underwater excavation, a painstakingly slow process that can cost hundreds of thousands of dollars. And if an excavation were to take place, archaeologists said they believed it would be the first in the Sea of Galilee, an ancient lake that boasts historical remnants spanning thousands of years and is the setting of many Bible scenes….

Much of the researchers’ limited knowledge about this structure comes from the sonar scan a decade ago. Initial dives shortly after that revealed a few details. In an article in the International Journal of Nautical Archaeology published earlier this year, Nadel and fellow researchers disclosed it was asymmetrical, made of basalt boulders and that “fish teem around the structure and between its blocks.”