Trajan's Column is a monumental triumphal column, which commemorates the eponymous emperor's victory in the two Dacian wars (102-3; 105-6). The column is almost all that is left standing of Trajan's Forum, the last of the imperial fora to be built in ancient Rome.
An inscription on the base states that the column was erected in honour of Trajan (r. 98-117) by the Senate and People of Rome ‘to show how high a mountain - and the site for such great works - had been cleared away’ (ad declarandum quantae altitudinis mons et locus tantis operibus sit egestus). This has been taken to indicate that the top of the column marks the original ground level, thus giving an idea of the extent of the excavations undertaken for the construction of the forum, which was funded by the spoils of war from the two Dacian campaigns.
The reliefs on the base depict captured Dacian arms and armour, while the torus at the foot of the column takes the form of a laurel wreath.
The shaft of the column is made up of blocks of white Carrara marble, which have been cut away on the inside to create a staircase that leads to the platform at the top. Around the shaft winds a frieze, 200 metres long and carved in low relief. The reliefs illustrate the story of the two Dacian wars in a continuous sequence of 155 scenes with over 2,500 figures (the emperor Trajan appears a total of 59 times).
The column once bore a bronze statue (5 metre high) of Trajan in military dress, but this disappeared centuries ago. In 1587 the statue of St Peter, the work of Tommaso della Porta and Leonardo Sormani, was erected.
In the 9th century a small church was built at the base of the column. San Nicola de Columna, which used the column as its bell-tower, was demolished in the 1550s.