Barrack The main single storey building is the barrack, its eight chimneys indicate its original accommodation purpose. The barracks are built into cut back bedrock and contain a row of single rooms used for military bunk-style accommodation for the lower ranks as well as accommodation for two separate officers' quarters. A central breezeway and vault covered staircase allows access from the barracks and lower terraces to the upper terrace battery, bastion and Martello tower. The two end rooms adjoining the barracks, known as the Tide Gauge Room to the north and the West Room to the south, were constructed soon after the completion of the barracks. The loopholes, or angled openings, were designed to enable the defensive fire whilst defending against enemy attack. Terrace The lower north west facing terrace is constructed on the same level as the barracks. It was probably built on rubble fill which is contained by a low stone wall.The terrace is open and not defensive in nature, as it faces away from the open sea and potential attack. It currently has a bitumen surface and several small planted garden beds. Garden beds were constructed on this terrace during the 20th century as part of the domestication of the fort by the Sydney Harbour Trust and later Maritime Services Board caretakers. Two sewerage treatment units which service the toilets are concealed in the garden beds at either end of the barracks. Plantings A Canary Island date palm (Phoenix canariensis) planted in one raised garden bed on the terrace's western side and a fruiting fig tree (Ficus carica cv.) at the south-west base of the Martello Tower are the only trees on Fort Denison.An external cannon is on the Eastern Terrace. A tall flag pole with side spars runs three permanently flown flags on this terrace. Condition As at 26 May 2014, the physical condition is excellent. Archaeological potential is high. Published material on such towers in the English speaking world suggests that this may well be the most intact tower. Modifications and dates The following modifications have been made to Fort Denison: 1840–1842 – construction of battery 1856–1858 – construction of battery, barrack and tower and bastion 1858–1862 – construction of terrace, west room and tide gauge room 1917 – construction of slipway Heritage listing Fort Denison was listed on the New South Wales State Heritage Register on 2 April 1999 . Tide gauge Tides have