(Photo: Marie-Louise Klaus)
This is a baobab tree near Wyndham, Western Australia. Like most baobabs, it has an enormous trunk. What makes it unusual is that it has a hollow center. It's a little living cave.
This proved handy to police in the 1890s who needed to lock up prisoners while out in the bush. That's why they temporarily sealed arrested suspects inside while awaiting more permanent housing. It has about 100 square feet of interior space, which was sometimes used to hold up to 30 prisoners at a time. An iron gate sealed people inside. That's why it's called the Wyndham Prison Tree.
There is another baobab near Derby, Western Australia, which is also called a prison tree. But its use as a prison is probably apocryphal.
-via Amusing Planet