Brisbane Observatory

Brisbane Observatory dates from 1805 to 1809. It is a small, symmetrical, single-storey, three-bay, private observatory building, possibly designed by James Gillespie Graham in a neoclassical style for the personal use of Sir Thomas Makdougall Brisbane (1773-1860) who was a pioneer of positional (navigational) astronomy.

The observatory is square in plan with a prominent bowed central bay to the south (the bow formerly supported a large dome). The building is currently roofless and has lost most of its interior but its walls are mostly standing to full height except at the south and part of the east wall (2018). Around the base of the building is an excavated channel covered with capstones (some are missing).

The south and east elevations are faced in finely droved ashlar and the remaining elevations are built of random rubble which retain evidence of previous harling. The ashlar elevations have fine deeply moulded cornices at cill height and at the eaves. The cill to the south has a circular carved imprint which is a setting for an astronomical instrument. There is also a blocking course remaining in parts. There is a blind ashlar window remaining to the east elevation.

The windows to the north entrance elevation have dressed stone margins with a projecting keystone; the doorway is pilastered and corniced.

The building's interior, seen in 2018, is a shell. The walls are stripped back to rubble and show evidence of being battened and covered with lath and plaster. There is the remains of a dividing wall to the north of the plan which separated the observatory room from a smaller retiring room with fireplace openings still in place.

There is a small, circular open rubble structure which is partially ruinous 11 metres to the southwest. It appears to be 19th century in date and is likely functionally related to the observatory.