It is, perhaps, a great irony that so little is known about one of the most iconic and instantly recognisable symbols of the ancient world. Built over three distinct phases, Stonehenge was begun 5000 years ago and was already ancient by the time the Romans arrived. Two different types of stone were used in the construction of the monument: local sarsen stones (weighing up to 50 tons each) and bluestones which were transported 240 miles from the Presceli Mountains in Wales. Much of what can be seen today originates from 3000 BC – 1600 BC, but the site was in use long before this. Carbon dating from post holes near the main circle have been Carbon 14 dated to the end of the last Ice Age, 10,000 years ago.