https://arkeonews.net/the-mysterious-prehistoric-underwater-structure-beneath-lake-michigan/
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About forty feet beneath Lake Michigan's glowing waters, Dr. Holley discovered stones arranged in a long line, over one mile in length.
The stones have been dated to approximately 9,000 years ago. That was 4,000 years before Stonehenge was built and approximately two thousand years after the Ice Age ended. It occurred when the lake bed was dry and before Grand Traverse Bay existed."