Stonehenge is a prehistoric monument in Wiltshire that is estimated to be over 5,000 years old.
What visitors see today is the product of archaelogical work to stabilise and re-erect the stones in the early part of the 20th Century, where for example in 1901 one of the sarsen stones and its lintel had fallen down, leading to the straightening of a large leaning trilithon.
Between 1919 and 1926 the south-eastern half of the monument was excavated and further work carried out to re-erect some of the stones, In the 1950’s further extensive excavation and renovation was carried out.
Thought you might like to see some images of these works. See these English Heritage document for more information on: the World War I Aerodrome, and Historic England reports, including one on Restoring Stonehenge.