Located in the Arakoon National Park just 5 kilometres east of the coastal town of South West Rocks.

The Trial Bay Gaol was established in 1876 as an experimental Public Works Gaol where the inmates would construct the breakwater. Although work started in 1877, it was not completed until 1886 due to difficulties in working the hard stone, inconsistent funding and contractual problems.

When the second (southern) wing of the gaol was completed in 1900, electric lights, a new kitchen, scullery, bakehouse, toilets, wash house and weather shed were installed in the complex, strongly indicating NSW Government support for the Public Works Gaol experiment. Yet only three years later work was abandoned and the gaol was closed in July 1903. Severe storms and increasing costs had seen only some 300 metres of the planned 1500 metre break wall completed. External buildings were auctioned in 1904, and after 17 years of use, the abandoned gaol remained as testimony to an experiment with humane prison reform. With the onset of World War 1, the old gaol was given a new lease of life as a German internment camp (1915–1918). After the war, a caretaker was installed and, with no foreseeable future, the gaol was stripped of all movable buildings and materials in 1922, leaving the heritage listed ruin that you see today.