The structure is about 30 meters in height. The shaft is made from a series of 18 colossal Carrara marble drums, each weighing about 40 tons, with a diameter of about 4 metres. The 200 meter frieze winds around the shaft 23 times. Inside the shaft, a spiral staircase of 185 stairs provides access to a viewing platform at the top.
The relief portrays Trajan's two victorious military campaigns against the Dacians; the top half illustrating the first (101-102), and the lower half illustrating the second (105-106).
The two sections are separated by a personification of Victory writing on a shield. Otherwise, the scenes on the frieze are continuous. The imagery is not realistic as the sculptor pays little attention to perspective. Often a variety of different perspectives are used in the same scene, so that more can be revealed (e.g. a different angle is used to show men working behind a wall).
The scenes depict mostly the Roman army in military activities such as setting out to battle and engaging the Dacians, as well as constructing fortifications and listening to the emperor's address. In all, 2500 figures are shown. The emperor Trajan, depicted realistically (not superhuman), makes 59 appearances among his troops.
It was traditionally thought that the Column was a propagandistic monument, glorifying the emperor's military exploits. But because the structure would have been generally invisible, surrounded by other buildings in Trajan's Forum, and simply the difficulty involved in following the frieze from end to end, it is now considered to have had much less propagandistic value.