The new study published in the journal Antiquity explains that Castell Henllys is a well-excavated hillfort in Wales which dates back to the late first millennium BC, in the Iron Age. In the 1980s, two experimental reconstructions of Iron Age roundhouses were built at the site. They were built on top of the locations of real Iron Age roundhouses and their construction was based on archaeological evidence recovered from the site. Castell Henllys. A view showing the entrance to one of the completed round houses in 1988. (Malcolm Neal/ ) The roundhouses have been key features of the heritage site, but health and safety concerns ordered that they could not simply be refurbished after 30 years, the roundhouse replicas had to be dismantled and rebuilt. In 2017/2018, the Pembrokeshire Coast National Park called in researchers to excavate the dismantled roundhouses. Originally, the archaeologists were interested in investigating the remains of the reconstructed Iron Age roundhouses to find out more about the decay process, how it impacts archaeological preservation, and which activities leave their mark on the archaeological record.