Setting things on fire.
I'd also had a go at making a Sanctuary shaped structure using very un-Sarcen like 'memorial' stones, plus tall and short posts.
This isn't to say that it is impossible to make accurate and 'interactive' Neolithic/Bronze Age structures using Gmod; but it is true that it would be hard work...Also, for the experience of entering the circle as if it were an arena, Gmod works best for people who are used to using a keyboard+mouse to navigate through virtual worlds.
And then I set things on fire.
I have a really strong image of the posts at Woodhenge being burnt rather than pulled down, or left to rot.
As I said before, what Terry Jones (Qur'an threatening minister) forgets, is that fire is sacred and -for people who beleive God to be within this world- a respectful way to destroy sacred objects