The town of Upton, Massachusetts, has taken possession of a mysterious man-made cave called the "Upton Chamber."
Barbara Burke, chairwoman of the Historical Commission, says the chamber is perhaps three centuries old. She bases that on an 1893 newspaper article, which states that elderly residents at the time said their ancestors had talked of the cave and and did not know who built it.Still others think it was built "under the influence of Irish monks in the 8th century."
Some say Colonial settlers might have used the chamber to store ice or vegetables. Others think it may have been a Native American ceremonial site. [Link]