The Mount Macedon Survey Cairn as it exists today is a large stone structure constructed of shaped and mortared stone. The structure is approximately 8 metres high and tapered from 4m diameter at the base to 1.5m at the top. The Mount Macedon Survey Cairn is one of the three examples in Victoria of mortared geodetic stone triangulation stations; the others being located in Mount Alexander and Warby North.
Mount Macedon had an early significance as a natural feature in centre Victoria, particularly as a directional landmark to travellers and settlers. Because of this dominance over social landscape, a trigonometrical survey mark was placed at the summit in 1853 and was later replaced at the mid to late 1860s.
The 1853 trigonometrical ground mark was typical of the times and consisted of a broad arrow cut into a flat stone, which was then buried some two to five feet below ground with a surface mark often placed for convenience. The cairn was deemed to have been the point from which all surveys in the district originated. Records confirm that Mount Macedon and other prominent hills in the vicinity of Melbourne were marked and cleared around 1853 by a team of British Engineers who were experienced in the Ordinance Survey of Great Britain.
In 1800’s theodolite observations on relatively clear hills, were taken from ground level, however on densely treed hills, such as Mount Macedon, a centre post was often erected to support the theodolite as such heights as to minimise the clearing. In such cases an independent staging was then built around theodolite support to allow the observer and the assistant to do their work without disturbing the alignment of the instrument. A removable flagpole was often employed to enable the station to serve as a sight from other distant stations.
Although the station had been marked by Royal Engineers under the supervision of Captain Clarke, it was not until August 1860 that the Macedon was observed from the main Geodetic triangulation and not until February of the following year that observations were taken at Mount Macedon.
The superintend of the Survey R.J.L. Ellery is said to have observed angles in February 1861 at Mount Macedon and again visited in March 1864.
The cairn was restored in 2016 for the enjoyment of future generations