The Racetrack Playa at Death Valley National Park is home to one of the most enduring mysteries. All across the bottom of this dry lakebed are hundreds of rocks that leave trails on the ground when they move. Some of the rocks, which weigh up to 700 pounds, have traveled over 1,500 feet. For years, the source of their movement had gone unsolved, but in 2014 researchers discovered a rare combination of events that move the rocks. When the California playa floods and cold winter nights freeze the water into a thin layer of ice that then break into large floating panels as night turns into day, winds drive the rocks forward across the slippery surface, which leave trails in the soft mud below. Although scientists have discovered the secret of the moving rocks, the fascination remains the same. With such a fragile surface, being careful to not leave tracks in this remote area will help keep it fascinating and mysterious for years to come. Photo by Shu Xu (www.sharetheexperience.org).