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Published November 07, 2013, 12:00 AM

John Ackerman


In this Oct. 10, 2013, photo, John Ackerman poses in a shaft entrance to his Temple of Doom, one of the 37 caves on his property near Spring Valley, Minn. Ackerman estimates he’s spent $4 million on cave exploration and acquiring underground rights, but he doesn’t charge admission to the nature groups, scientists and cavers who visit. It’s a hobby made possible by his successful furniture restoration business, he said. (AP Photo/Jeff Baenen)
Read the article: Minnesota man's cave collection is his hobby, passion