Granite blocks are seen in Amapa, Brazil, on May 10, 2006. A grouping of 127 granite blocks along a grassy Amazon hilltop may be the vestiges of South America's oldest astronomical observatory, according to archeologists who say the find challenges long-held assumptions about the region's prehistory. Farmers and fishermen in the region have known about this site, which local press reports have dubbed the 'tropical Stonehenge' for years, but archeologists only became aware of it thanks to a geological survey carried out in the region earlier in 2005. Scientists not involved in the discovery said they believed the site could provide a valuable key to understanding pre-Colombian societies in the Amazon. (AP Photo/GOVERNO DE AMAPA, Gilmar Nascimento)
