DEGANIA ALEF, Israel — A stone structure over 10 meters high and 70 meters wide surprised scientists when it was was found submerged beneath the Sea of Galilee. Essentially it's a giant pile of rocks, but when it was built and why it's there have been unanswered questions.

But recently published research has put forward a couple ideas about exactly what its purpose was: It could be a cairn, or in layman's terms, a giant pile of rocks that designates a burial site; Or it could be a way of attracting fish to make catching them easier.

Regardless, it's pretty clear that the structure, discovered in 2003, is man-made, though it shows no signs of construction in the traditional sense.

"Close inspection by scuba diving revealed that the structure is made of basalt boulders up to 1 meter long with no apparent construction pattern," the researchers wrote. "The boulders have natural faces with no signs of cutting or chiselling. Similarly, we did not find any sign of arrangement or walls that delineate this structure."

But just because it's a pile doesn't mean it has no purpose. Fish nurseries made of piled stones are not uncommon in the Sea of Galilee, spaced out a regular intervals along the shore, according to the a study. But those are mostly smallish, only one or two meters across.

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The latest discovery is truly massive, weighing in at over 60,000 tons. That's one big fish nursery. And it makes some sense, since fish do seem to be found around the structure, according to the report.

If it's a fishery, it was probably built by dropping stones into the water, meaning it has always been under the sea. But the other possibility — that it is a burial site — means the structure was originally on land and the shoreline or sea level changed over time, covering it in water.

How old the site is is a matter of debate as well. There are other stone structures nearby that date to the early bronze age, as well sites of ancient villages. That puts it at about 4,000 years old. But based on sediment, accumulation, it could be as old as 12,000 or as young as 2,000.

"The only period in this region for which megalithic structures can be connected to settlement sites is the Early Bronze Age, between the late 4th and the late 3rd millennia BCE," the report states. "The monumental site of Khirbet Beteiha, located some 30 km north-east of the submerged stone structure, comprises three concentric stone circles, the largest of which is 56 m in diameter."

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