I also think Stonehenge is an amazing architectural structure that is important to preserve and study. I enjoyed reading in your blog all the different theories of it's existence. I have heard before that its purpose might have been for ceremonial rites, religious sacrifices, and also some type of ancient calendar. But I was unaware and very entertained by the fact that it might hold some kind of "magic powers" and that as you stated "... medieval Britons thought that only the magic Merlin could have assemble the stones of Stonehenge." 
I agree with you that Stonehenge is an important part of a time capsule because of its mystery and also because of how  fascinating it is that man transported these massive heavy stones to its location without the use of the wheel and other useful technology. I also think this ancient unique structure is important because of its anonymity, it keeps historians, astronomers, and other types of scholars interested in our past and searching for answers, while trying to uncover the answers of Stonehenge, I think other questions of our past can be discovered.
Out of all the theories you researched which one do you personally  believe in, if any and why?
also something kind of cool and funny...just outside my hometown in Virginia on top of a hill in the middle of nowhere there is a life size replica of Stonehenge, made completely out of foam...its called "foam-henge" it's actually a really cool thing to see in person and lets you realize how huge the stones actually were. google it if you are interested, its pretty neat:)