Consisting of a ring of monolithic stones, complete in some cases with heavy stone lintels, argument has long waged between historians and scholars as to both the site's construction and its purpose. The Neolithic period in which Stonehenge was erected was initially thought to have lacked the means of transporting and lifting the 25-50 ton stones that now stand and lie at Salisbury Plain. Built over a period of 650 years, both supernatural and methods deemed out of their time have been suggested as being behind the construction, although more recent claims have argued that it could actually have been carried out by hand using primitive technology and the principles of leverage. Theories as to Stonehenge's function have ranged from a Druidic place of worship and sacrifice; an observatory; a burial ground; an extraterrestrial landing site; right through to the latest evidence that it was in fact a place of healing in the vein of a stone-age Lourdes.