The structure is about 30 meters (98 ft) in height, 38 meters (125 ft) including its large pedestal. The shaft is made from a series of 20 colossal Carrara marble drums, each weighing about 40 tons, with a diameter of about 4 meters (13 ft). The 190 meter (625 ft) 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.
According to coins depicting the column, it was originally topped with a statue of a bird, possibly an eagle, and later by a heroically nude statue of Trajan himself. In 1588, it was replaced by a statue of St. Peter (which still remains) by Pope Sixtus V.