https://www.newscientist.com/article/dn310-concrete-evidence...
Most of the one million visitors who visit Stonehenge on Salisbury Plain every year believe they are looking at untouched 4,000-year-old remains. But virtually every stone was re-erected, straightened or embedded in concrete between 1901 and 1964, says a British doctoral student.
These photos may be good evidence of realignment and alteration since the big sarsen falls in the eighteenth century.