Woodhenge

Just a short distance away from Stonehenge, is the Neolithic monument of Woodhenge. It was excavated between 1926 & 1929 and is made up of 168 post holes, in six concentric rings, that would have held mainly wooden posts, some as tall as 9 feet. 

So that you can see the rings, small concrete posts have been put into each of the holes. It must have been a formidable monument in its day.