Notes taken from Wikipedia.
Adansonia gregorri, commonly known as the boab, is a tree in the family Malvaceae. As with other baobabs, it is easily recognised by the swollen base of it's trunk, which forms a massive caudes, giving the tree a bottle like appearance. Endemic to Australia, boab occur in the Kimberley region of Western Australia (WA), and east into the Northern Territory (NT). It is the only baobab to occur in Australia, the others being native to Madagascar (six species) and mainland Africa and the Arabian Peninsula (two species). Boab ranges from 5 to 15 meters in height, usually between 9 and 12 meters, with a broad bottle shaped trunk. It's trunk base may be extremely large, trunks with a diameter of over five metres have been recorded. A. gregorii is deciduous, losing it's leaves during the dry winter period and producing new leaves and large white flowers between December and May.
The Boab Prison Tree, Derby WA, is a large hollow Adansonia gregorii (Boab) tree just shouth of Derby, WA. It's reputed to have been used in the 1890's as a lockup for indigenous Australian prisoners on their way to Derby for sentencing. It is now a tourist attraction.
In fact, there is no evidence that the Derby Prison Tree was ever used for holding prisoners.
The photo was taken on the way to Broome,WA