As a coach load of American tourists on a visit to England drove through Wiltshire, the guide was busily pointing out places of interest. When they approached Stonehenge, the guide announced: "This is Stonehenge, a megalithic monument dating from about 2,800 BC. It consisted originally of thirty upright stones, their tops linked by lintel stones to form a continuous circle about a hundred feet across. The uprights were built from local sandstone, and each stone weighs around twenty-six tons." At the back of the coach, one tourist turned to his wife and said: "Pretty impressive, huh?" "Yes," she agreed. "But wouldn't you think they'd have built it further back from the main road?"