The Umpherston Sinkhole is located in Mount Gambier, South Australia.

We stopped there on our way between Warrnambool (VIC) and Robe (SA).

It is a naturally formed sinkhole that was transformed into a garden back in the 1880's.  You can view the sinkhole from a number of vantage points around the top, but there is also a path that spirals all the way down to the bottom of the sinkhole.

As you descend, it is like walking into a different place and time.  The outside world disappears and you could easily be in some magical fantasy garden.

Well worth a visit if you are in the area.