Technically Stonehenge is not an henge (even the term henge comes from Stonehenge)

> Ironically, even though Stonehenge has an earthwork circle around it (the earliest phase of the monument), it isn’t officially a ‘proper’ henge, as the main ditch is external to the main bank. It has to make do with being a ‘proto-henge’.

https://www.english-heritage.org.uk/visit/inspire-me/what-is...