Castell Henllys is a reconstructed Iron Age village, or fort, but the only one in Britain built on an original Celtic site. So the idea is that you walk in the footsteps of the Demetae tribe that lived there 2,000 or so years ago. It is very much geared to schoolchildren, but it is fascinating for all ages. As well as roundhouses, enclosures etc, there is a visitor centre and you can stroll through the surrounding countryside and take a picnic. Regular events are held.