This research concerns Mada'in Salih, an archaeological site in north-west Saudi Arabia. Historically, it was part of the Nabataean kingdom which flourished in northwest Arabia (Jordan, parts of Syria, Palestine and some parts of Saudi Arabia), with Petra in Jordan as its capital. The Nabataeans were famous for their trading role, as they transported frankincense and myrrh and exported balsam and bitumen. They built monumental tombs in Petra and Mada'in Salih as well as other public buildings such as temples theatres and baths. They were also famous for their skills in hydraulic engineering and the production of very thin, distinctively painted pottery. Mada'in Salih was an important station on the trade route which linked south Arabia with...