There are actually two mysteries surrounding Stonehenge. One is how 30 enormous sarsen stones were moved from their original location, arranged upright in a circle, with a ring of 30 additional lintel stones placed on top. Each of these stones is about 13 feet high and weighs about 25 tons! Within this circle are additional stones forming a horseshoe shape.
Mystery number two...exactly what did the ancients use Stonehenge for? Several theories have been proposed including an astronomical observatory for the summer solstice, the longest day of the year (which is 21 June 2009...the day before our visit). This event brings thousands to the site for the annual celebration to watch the sunrise. (Hopefully, they will be partied out by the time we arrive!)
Another theory is that Stonehenge was used as a religious site...hence the horde of "Druids" that descend on the area during summer solstice.
Most recently it is believed to have been a burial site and/or healing site as cremated remains dating back to 3,000 B.C. were unearthed there in May 2008.
In answer to the most asked question: No, we will not be able to walk among the stones, but we will be able to walk around it. But if you'd like a virtual tour inside the stones, go here for a 360 degree view from the inside by moving your cursor around inside the picture. For more information, see the official Stonehenge web site.