The hard grey stone is one of the most durable materials available and helps to explain why the city's buildings look brand-new when they have been newly cleaned and the cement has been pointed.
Union Street runs for 0.8 miles (1.3 km), is 70 feet (21 m) wide and originally contained the principal shops and most of the public buildings, all granite.
Part of the street crosses the Denburn ravine (utilised for the line of the Great North of Scotland Railway) by Union Bridge, a fine granite arch of 132 feet (40 m) span, with portions of the older town still fringing the gorge, 50 feet (15 m) below the level of Union Street.
Designed by Peddie and Kinnear and built between 1868 and 1874, it is one of the most splendid granite edifices in Scotland, in Flemish-Gothic style in recognition of close trade links between Aberdeen and Flanders, it contains the great hall, with an open timber ceiling and oak-panelled walls; the Sheriff Court House; the Town and County Hall, with portraits of Prince Albert, the 4th Earl of Aberdeen, various Lord Provosts and other distinguished citizens.
In the vestibule of the entrance corridor stands a suit of black armour, believed to have been worn by Provost Sir Robert Davidson, who fought in the Battle of Harlaw in 1411.
On the south-western corner is the 210 ft (64 m) West Tower, with its prominent bartizans, which commands a fine view of the city and surrounding country.
This building, with its imposing corner entrance of four giant order composite columns, and statue of Ceres above, is now a pub named after its original architect.
At the upper end of Castlegate stands The Salvation Army Citadel, an effective castellated mansion, on the site of the medieval Aberdeen Castle.
Marischal College and Greyfriars Kirk on Broad Street, opened by King Edward VII in 1906, is the second largest granite building in the world (after the Escorial, Madrid), and is one of the most splendid examples of Edwardian architecture in Britain.
The architect, Alexander Marshall Mackenzie, a native of Elgin, adapted his material, white granite, to the design of the building with the originality of genius.
The large kirkyard of the Kirk of St Nicholas is separated from Union Street by a 147 ft (45 m) long Ionic façade.
Of note are eight tower blocks constructed between 1959 and 1977 which were Grade A listed in January 2021, on account of their "outstanding architectural quality and historic interest".
The Masonic Temple in Crown Street, with its distinctive open pediment, designed by Harbourne Maclennan, Jenkins and Marr, and constructed in 1910, is an example of Edwardian Baroque architecture.
Lord Byron's bronze statue, by Pittendreigh MacGillivray stands in grounds of Aberdeen Grammar School in front of the original main entrance.