I watched a documentary about Stonehenge tonight, and it proposed the theory that the location for Stonehenge was chosen because of a natural geological feature in the area.

There's a man-made path that proceeds south-west towards Stonehenge: "The Avenue". This path was built around the same era as Stonehenge itself. If you walk westward along The Avenue on the winter solstice, you'll be facing the point on the horizon where the sun sets. However, under The Avenue, there's an old natural geological formation from the time of the Ice Age: a series of ridges in the rock which just coincidentally align with the sunset on the winter solstice (an "axis mundi"). Before Stonehenge was built, there was a chalk knoll on that location. That meant that you could walk along a natural geological path towards the sunset on the shortest day of the year, and there was a local geological landmark in front of you.

The theory is that these natural geological formations coincidentally aligning with an astronomical phenomenon made the site a special one for early Britons. That's why there was a burial site there, and later Stonehenge was built there.

Here's the article by the archaeologist who discovered the Ice Age ridges: Researching Stonehenge: Theories Past and Present