This is a beautifully bleak place. Its well worth the money to the NT to just have a wander round the ruins, and get the amazing views from the top. Prehistory wise there isn't that much to see except the mound itself and at least 5 barrows within view from the top.
The whole area does oooze of the 'mother spirit' however and its not hard to imagine this hill being revered, standing solitary as it does between the two huge banks, that seperate Purbeck from the world.
Traditionally Edward The Martyr was killed here by his wife Elfthryth, before the castle (that we see now) was built. So most likely it became a place of pilgrimage. Or perhaps the story pre-dates the event and so does the site.
Once going there I undertook the steep climb to the nearest portion of the bare hill on the other side of the road from the castle itself. Despite the meagre evidence about me I could not shake the feeling that this was the prior site in this vicinity, only later being purposely slighted by the building of Corfe Castle opposite. I too felt the presence of giants two, only mine were lying down head to head chatting, their bodies going down the respective hills .
An excellent place to appreciate this womanly view is at the Scott Arms (raised up on a hill opposite, further into Purbeck) with a pint of beer in your hand (check it on the 'facilities' menu). Also I can vouch for their puddings.
If like me you're wondering, "why is a Norman castle on this Web site?", the missing bit of information is a referrence to the castle mound (not the castle itself) in the Modern Antiquarian book:
"Crossing Middlebere Heath, the mound of Corfe Castle rises up between its two hill ridges like a divine Mother hill. When I visited Corfe Castle in May 1996ce, I saw that the castleless mound had once represented the Mother lying on her back, the East Hill and West Hill representations of the open legs and the central mound as great clittoris, womb and belly all together."
Thanks to Holy McGrail for pointing this out. I must read the book from cover to cover 'cos I keep missing these things!