Queensland State Archives posted a photo:
The fort is a typical nineteenth-century garrison – a pentagonal fortress concealed behind grassy embankments – surrounded for greater protection by a water-filled moat. Approval for construction of the fort at Lytton was given by the Parliament of Queensland in 1878. A field force of field artillery, engineers and infantry were also established to defend against a land attack by enemy forces. The government did not favour cavalry, as mounted soldiers could be recruited from the police force in an emergency. A small marine defence force was also developed, consisting of the two gunboats Gayundah and Paluma, the torpedo boat Mosquito and a number of armed barges.
Description source:
Wikipedia
View the original record at the Queensland State Archives:
Item ID 2692229