When you think of ancient, stone-age megaliths, the most likely thing that will pop into your head will be Stonehenge. It’s an amazing structure, and the techniques used to move and put up the stones in the first place is uncertain, in part because of a lack of written records (but neither Merlin nor aliens are likely to have been involved). It has also been long recognized for having not only a religious or ceremonial role, but also acting as an astronomical tool of sorts. There are also burial sites surrounding the structure.
So, when you think of Stonehenge, you would think it would be a prime example of a henge in the language of archaeologists. But it’s not. A henge is defined as a circular earthwork with a ditch on the inside surrounding a flat area with at least a 20 meter diameter. But instead, at Stonehenge this ditch is outside the circular earthwork bank. And that is just great, isn’t it? The most likely example of what people would think of as a henge is in fact not typical. Which only confirms what I fear about all nations: they have things simply to confuse foreigners. (Think about it: how many people must be confused when they come to the US and are told to put their John Hancock on the paper? Customs must get really awkward.)
Now Woodhenge, on the other hand, is actually a henge and not far from Stonehenge. The two were also potentially connected in ceremonies, but if we have learned anything from the above, there is no such thing as wood.