
Western Australia's Parliament House is in the background of this photo but is obscured by the Barracks Arch.
The Arch is all that remains of the Pensioner Barracks which were built to house the soldiers (and their families) of the Enrolled Pensioner Forces, as well as some retired veterans who had been honourably discharged from the British Army. They were sent to WA to guard the convicts that were transported to the colony from 1850 to 1865.
The government started to demolish the Barracks back in the 1960s to make way for the new Parliament House and the Mitchell Freeway, however, vigorous protest from the public resulted in most of the Barracks being torn down, but the Arch retained and restored, thus spoiling the politicians' view down St Georges Terrace (which is where I am standing on the median strip taking this photo).