South Australia · Natural Wonder
Umpherston Sinkhole
The Sunken Garden in a Collapsed Limestone Cave
schedule 1 min read / Updated Apr 2026
A limestone sinkhole in the centre of Mount Gambier turned into a terraced sunken garden by James Umpherston in 1886. The garden is illuminated at night and is often visited after dark when possums emerge from the surrounding vegetation.
The Umpherston Sinkhole, also known locally as The Sunken Garden, is a collapsed limestone cave on Jubilee Highway East in the centre of Mount Gambier. The sinkhole formed when the roof of an underground chamber gave way thousands of years ago, leaving a bowl-shaped depression around 20 metres deep and 50 metres across. Its walls are sheer limestone, ferns and climbing vines, and the floor is a terraced garden.
The garden was created in 1886 by James Umpherston, a local landholder who owned the property at the time. He had terraces cut into the sides of the bowl, built a staircase down to the floor, and planted hydrangeas, ferns and English garden species that thrived in the cool shaded microclimate. After Umpherston's death the garden was neglected for decades, but it was fully restored by the South Australian government in the 1970s and 80s and is now one of the most visited sites in Mount Gambier.
The sinkhole is open to the public 24 hours a day, free of charge. It is floodlit at night and the after-dark visit is the signature experience for most travellers, because the resident ringtail possums emerge from the ivy on the walls to forage across the terraces. The sinkhole can get crowded in peak summer afternoons, but is almost always quiet in winter mornings and after 9pm.
Scenic views
Lookouts near Umpherston Sinkhole.
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Attribution
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Images (3)
- (AUS-South Australia) Umpherston Sinkhole 2025-12-11.jpg · S5A-0043 · CC BY 4.0
- MountGambierSinkhole.JPG · Mattinbgn · CC BY-SA 3.0
- Portrait of a Naughty Possum.jpg · Gwendolyn Taunton · CC BY-SA 4.0
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