Segesta's Doric temple is one of western Sicily's great classical sights, standing almost complete on a hillside outside Calatafimi Segesta. It was begun by the Elymians in the 5th century BC and never fully finished, which is part of its fascination: the columns still carry the clean force of a Greek temple without the later clutter.
The setting matters as much as the stone. The temple sits alone among fields and hills, with enough space around it to feel dramatic rather than museum-like. Go early or late if you can; the light is kinder and the tour-bus rhythm is easier to avoid.