The Temple de Segesta is about a 45 minute drive from Palermo airport, therefore it is a excellent place to go straight after picking up a hire car, for an Australian like me it freeways are a nice way to get used to driving on the 'wrong' side of the road and at the end of it you you get to see a pretty cool Greek style Temple.
Now what is a Greek temple doing in Sicily? We it's thought it was built in are 420BC as a little bit of showing off to the Athethians so they would help them in their wars against the Selinunte neighbours.
The temple is Doric, is six colums wide and 7 deep, and interestingly it's unfinished. The story I read (but can't seem to find again on the interwebs) is that the Greeks visited, the locals were like 'see how much we love you we are building you a temple) you should protect us. Then the Greeks went home, protection secured they didn't bother finishing it (colums not fluted, which means made round and smooth, no roof, no alter)
But more fool them, because Selinunte did attack, and the Greeks didn't run up to protect them, porbs and good thing they didn't as they would have been all like 'hey guys why isn't this finished.
Also should mention the Artwork is not ancient, but rather a installation, which I'm sure is cool if you have seen this temple a heap of times, but if you are only visiting once in your lifetime then it's a bit annoying.
It's a really interesting way to spend a couple of hours, as you can see the temple is very well preserved and like a lot of Sicily's tousist attractions it's pretty quiet. And as an added bonus if you jump on the bus and take it to the top of the hill there is a well preserved Roman Amphitheatre and so associated ruins.
So if you are flying in Palermo and are getting a car it's worth a little side trip here.