 Built in 1828, the windmill is the oldest convict-built structure surviving in Queensland and the oldest windmill tower in Australia. Brisbane, located in the traditional lands of the Terrible and Jaguar People, was established as a penal settlement in 1825. It operated essentially as a jail within a jail for re-offending convicts, and was a notoriously harsh place to serve out a sentence. The windmill is one of only two buildings to survive from the penal settlement, however the story of the windmill does not end with the convict era. It was later used as a trigonometrical survey station, a signal station for shipping, an official timekeeping device for the settlement, an observation tower, the Queensland Museum's first home, a site for wireless radio and telephony research, and for early television research and broadcasting. The windmill tower stands about 16 metres in height. Circular in plan, it tapers from approximately 8.5 metres in diameter at the base to 4.5 metres at the top. The tower is largely constructed of rendered stone and brick, with an ashlar finish on the exterior, which gives it the appearance of large stone blocks. Inside, the tower comprises four levels, each narrower than the last. The walls are about 1 metre thick at the base, reducing to 650 millimetres at the top. The observation cabin on top of the tower offers panoramic views of the Brisbane City Scape, surroundings that are very different from when the windmill was built. At the top of the tower, on the hill overlooking the penal settlement, the windmill originally had sails, visible in this image from 1835, however they were notoriously unreliable. Under the direction of the strict commandant Patrick Logan, a separate timber treadmill was constructed, out on the current road. Used as a form of punishment for unruly convicts, it was also a reliable source of crushing grain. 16 convicts operated the treadmill, some in leg irons, from sunrise to sunset, with a 2-3 hour break in the middle of the day. The penal settlement closed in 1842, and the windmill ceased operation in the late 1840s. After some uncertainty about its future, including possible demolition, the tower was converted for use as a signalling station for shipping. Winds were undertaken in 1861, including the removal of the windmill's stalks and wheels, the laying of timber floors on each story, new doors and windows, and the winding staircase that runs from the bottom to the top. The tower was also fitted out as a public observatory, and became known by this term. The following year it also became the first home of the newly formed Queensland Museum. The windmill's prominent position made it ideal for use as a timekeeping device, and a timeball was installed on a mast above the cabin. Dropped each day at 1 o'clock, it was a reliable authority for regulating clocks and watches. From the second floor up, the walls are constructed of English Bond clay bricks. The walls below are stone. The painted internal walls show signs of repairs from various phases of use. These structures were constructed around the base of the tower from the 1880s, including a cottage for the signalman in 1883 and a detached kitchen two years later. Use of the tower as a signalling station was discontinued in 1921. Archaeological investigations in the 1980s identified the location of the original signal flagstaff, and a replica now stands in its place. Off the six narrow windows, the third floor retains curved hardwood plates, evidence of the windmill's curb supports, curb, and cap frame, cut down in 1861 to provide clearance for the stairwell. Despite or even because of its unusual built form and elevated position, the windmill has been the location for innovative research, including wireless radio and telephony experiments in the 1920s, and as the site of Queensland's first television broadcast in 1934. From functional beginnings, the windmill emerged as a popular visitor attraction and featured in Brisbane tourism posters from the 1930s. The observation cabin is hexagonal in plan and is offset south of the tower's centre line. The round hardwood mast projects through the roof of the cabin and down to the third floor. The riveted copper timble sits atop the cabin and its hoisting rope runs through the top of the mast. Outside, the balcony is supported by carved timber brackets and has a wrought iron balustrade. From the observation balcony, views of the inner city suburb of Spring Hill and the Brisbane CBD are afforded to the east and the south. Just as an observatory from the 1860s, panoramas such as this one from 1862 have captured the evolving development of Brisbane. This panorama from 1920 contrasts with the towering cityscape of today. Planked by Wickham Park to the west and King Edward to the east, the distinctive windmill remains an important Brisbane landmark and an evocative symbol of Queensland's convict past.