You have to marvel at the determination of prehistoric man when you look at Stonehenge. Construction started about 3000 BC on what was originally burial grounds. Huge monoliths, weighing 25 tons, were dragged 240 km (150 miles) to the site a few hundred years later. It’s not known exactly how many humungous rocks were moved to a field near Amesbury but there are 13 standing today. It’s also not known why Stonehenge was built, but many believe this great UK landmark is associated with early astrology.