Stunned couple unearths 150-pound mystery hidden beneath their backyard for decades

A couple in San Francisco recently unearthed a 150-pound limestone sculpture buried in their backyard — setting off a search to uncover who created it and how it got there.

Greg Gatwood was doing yard work at the couple's Russian Hill home in May when he came across what he initially thought was a piece of concrete buried in the ground as his partner Judy Gittelsohn stood nearby.

Gatwood told Fox News Digital he tried to pry the object loose with a shovel before grabbing a pickaxe ...