This is one of the best UNESCO sites I have visited, it is on a huge scale and very well preserved. The theatre and Capitol are almost entirely intact! And the size is so impressive. The remote location really adds to the appeal as well set on the side of a hill overlooking mountains and cornfields. If you are in Northern Tunisia this is a site really not to be missed.
To get there catch a bus or Loauge from Tunis to Terbosouq (these normally carry on through to Le Kef) from here the locals can help you to get to the site, but chances of bartering may be low as there seems to only be a few taxis around for tourists, so expect to pay about 15TD (€9) for a taxi/ caminette so the more people going the cheaper it will be! It is about 15km away and pretty remote so it is money well spent, you may be able to get it cheaper if you go in summer and try a bit of bartering!