Tucked away in a small patch of southwestern Minnesota prairie is one of the state's enduring mysteries. Centuries ago people carved thousands of symbols into rocks near the small town of Jeffers. Who were they, and why did they painstakingly carve petroglyphs of animals and other figures? This summer archeologists will take another crack at answering the questions. But in the meantime, the site is becoming a hot spot for visitors interested in the carvings.