Cave Gardens, Garden and show cave in Mount Gambier, Australia.

Cave Garden / Thugi is a 30 m (98 ft) deep limestone sinkhole in central Mount Gambier, ringed by a formal garden laid out between 1906 and 1910. A scenic walk and a lowered viewing platform look down into the sinkhole; the cave floor itself cannot be reached. In wet weather, drains at the top of the sinkhole send a waterfall down into the cave.

The site was discovered by European settlers during a survey in 1845-46 and served as the main water source for the growing town until the 1850s. This early importance for water supply shaped Mount Gambier's development in its first decades.

The site was renamed in 2022 to Cave Garden / Thugi, with Thugi coming from the Bungandidj language meaning bullfrogs. This naming choice honors the connection between the place and its Indigenous peoples and their relationship with the natural world.

The cave floor itself cannot be reached; visitors view the sinkhole from a lowered viewing platform reached by a scenic walk through the garden. After rain, the drains at the top of the sinkhole feed a waterfall into the cave, so wet weather is the time to see it. The garden sits in the centre of Mount Gambier, beside the site of the town's first post office, Town Hall and hotel.

During wetter seasons, water flows down the limestone walls of the sinkhole creating a natural waterfall in the middle of the town. This phenomenon shows how underground water systems become visible at the surface with changing seasons.