Built in 1864, this hefty octagonal building with a central courtyard was once the Aboriginal prison block. During its time as a prison several men would share a 3m by 1.7m cell, with no sanitation (most of the 300-plus prisoner deaths here were reportedly due to disease; at least five people were executed). The only part of the complex that can be visited is a small whitewashed chapel, where a weekly Sunday service is held at 9.30am.
Karma Rottnest lodge still occupies part of the Quod; the long-term future of the hotel on this site is uncertain.