Blackford Hill lies 2 miles (3 km) south of the centre of Edinburgh and rises to 164m (539 feet). Prominently located on the hill is the green-domed Royal Observatory, which includes the Institute for Astronomy of the University of Edinburgh. The grand red sandstone archway at the entrance to Observatory Road was built in 1887 to commemorate Sir George Harrison, Lord Provost and Member of Parliament for Edinburgh South, who had died two years previously. It was Harrison who facilitated the purchase of 43 ha (107 acres) of the hill by the city in 1884 to make it available as a public park.
Blackford Hill is composed of Lower Devonian volcanic rocks, lying between Upper Devonian sandstones, representing the northernmost extent of those found in the Pentland Hills. Thus, geologically, this hill is rather different from the Carboniferous volcanic plugs and intrusions which form the remainder of Edinburgh's hills (with the exception of the Braid Hills). Also of geological interest is Agassiz Rock, situated close by in Blackford Glen, which was the first evidence of the action of glaciers to be found in Scotland, recognised by the Swiss geologist Louis Agassiz (1807-73).
The residential area of Blackford lies to the northeast and Craigmillar Park Golf Course and the King's Buildings Campus of the University of Edinburgh lie to the east. Blackford Pond to the northwest lies adjacent to Cluny Gardens and to the southwest are the Hermitage of Braid and the Braid Hills.