don't forget to drop in at old sarum, well worth a look: only the foundations of the old cathedral and the castle remains are poor, just the inner course of walls with the dressed outer stones pinched , but all set within an impressive ironage hillfort, there is an entrance fee (english heritage)

the medieval cathedral is well worth a look in, go and stand under the crossing under the tower and look up and marvel at how much the stone pillars have twisted under the weight of the spire above (they weren't designed to carry the weight as the spire was added later) also if you go right up to the east end to the lady chapel, there are free standing columns made of polished purbeck stone in groups of four, about 40ft plus tall but ever so slender carved in single lengths of stone.

great cathedral built in only 40 or so years, all in one style (early english, hmmmm such clean lines, stiff leaf foliage on capitals of columns).

...oh hang on, i seem to be on the wrong forum.

there's also a museum there i believe with stonehenge finds.

don't forget to head south and drop in at knowlton henges (no entrance fee limited parking) and if you manage that go and find the Dorset Cursus, it's a little bit up and to the left, not strictly wiltshire but close enough to make the effort