the lossal h anorted to the comnityusm tenochtitlan. so now, with the help of the town, 're building a better home for all the sculpture we have housed there. obregon: these portraits are carved of stone in a region where stone is not naturally available. enormous blocks of basalt weighing many tons apiece were carried witut beasts of burden some 60 miles from distant mountains. the magnitude of this task is clear evidence of the ruler's power and authority over a large and efficient labor force. olmec culture at san lorenzo declined around 900 b.c., perhaps because of environmental change, warfare, or competition from other sites. whatever the cause, the demise of san lorenzo cocid with the re of another olmec cter, la venta. located near tulf coast on high ground surrounded in ancient times by swamps and rivers, la venta floished from about 900 to00 b.c. this hill is actuay a manmade mounta of earth, pack io theshape of pyr. the pyramid is the focus of a who complex of smallerthen mounds, carefully consucted on a north-south axis to f