This photograph shows the guardhouse that was originally part of the entrance to Government House in the Royal Botanic Gardens, Sydney. The building was completed in 1848 and is thought to have been built by the Colonial Architect Mortimer Lewis. The guardhouse was in the Gothic Revival style and resembles a small castle with its tower and arched windows. The building was originally on Macquarie Street but was moved back in 1915 when the Sydney Conservatorium of Music moved into the former stables (Greenway Building) to provide public access.
For more on the guardhouse see http://collection.hht.net.au/firsthhtpictures/picturerecord.jsp?recno=39021