Baobab / Boab Prison Tree - a very ancient but hollow Boab with an opening through which one can climb inside (Adansonia gregorii). Derby, Kimberley Region, Western Australia, Australia. This tree is believed to be about 1500 years old. It was used as a staging point for prisoners being walked into Derby in the early days. The prison tree is a registered Aboriginal Site and one of the main tourist attractions around Derby. This kind of tree has special abilities to store water and is a typical feature of the dry Kimberley landscape.