Archaeologists and other experts began digging at this central Bosnian town last week to explore the team leader???s theory that the 2,120-foot hill covers a step pyramid, which would be the first ever found in Europe. ???These are the first uncovered walls of the pyramid,??? Semir Osmanagic, a Bosnian archaeologist who studied the pyramids of Latin America for 15 years, said of the stonework foun