Stonehenge is a landing-pad for alien spaceships, built by the ancient Druids, in consultation with their alien masters, on a powerful intersection of ley lines running towards Atlantis and El Dorado.
Seriously, Stonehenge is a megalithic structure in the United Kingdom. Archeological investigation and dating has given a best guess that it was built and re-embellished in about three different phases between approximately 3000 BCE and 2000 BCE. The bottom line is that nobody knows for certain why it was built because the people living there didn't know how to write. (Writing was only introduced to Britain by the Romans in 49 CE, some two millenia after Stonehenge was finished!)
Some believe Stonehenge has supernatural origins and some neopagans think was a place of worship for the "old religion." Archeologists note the monument is older than the Druid religion which dates from the Iron Age, but this has not kept various theories linking Stonehenge to the Druids from proliferating. This is, however, dispelled by the fact that Stonehenge was built 2000 years before Druids first arrived in the area. While some archeologists would like to think Stonehenge had just a singular purpose, many neopagans believe that it probably had multiple purposes, because it is designed to align with multiple events (such as the lunar cycle). The latest theory is that the monument was built to celebrate a grand act of union between previously warring tribes.
Currently, the monument is aligned so that the sun rises from behind the "heel stone" on the midsummer solstice. This leads some to claim Stonehenge as a kind of 'ancient observatory'. Further shades of woo are indulged in by Velikovskians and other pole shift enthusiastics, who in various attempts to both have their cake and eat it, will claim that the fact the heel stone was moved means the earth's orbit and/or pole must have moved, or conversely the fact that the heel stone hasn't been moved means that the earth's pole/and/or/orbit must have moved just before Stonehenge was built and they built it to measure the new seasons.
Something interesting about Stonehenge is that is partly made out of a blue stone called, creatively enough, bluestone. Bluestone had to be brought from over a hundred miles away, possibly by sea, or more likely levitated into place by Merlin. Hang on a minute, that can't be right... look — it's Julian Cope!
It should probably also be pointed out that the ancient Britons built megalithic structures, dolmens and stone circles all over the British Isles and north west Europe. As architectural fashions demonstrably change over the years, it is always possible that they simply thought they looked pretty damn cool.
 See also
- Georgia Guidestones: A faint imitation of the original.
- ↑ Sheffield university helps to crack the mystery of Stonehenge - possibly, The Guardian, 22 June 2012
- ↑ Actually, the word "henge" is derived from the name Stonehenge. Even though Stonehenge isn't one. The name Stonehenge was coined by 11th-century English writers, and just meant "supported stones".