Trajan's Market (Mercatus Traiani) is a large complex of ruins in the city of Rome, located on the Via dei Fori Imperiali, at the opposite end to the Colosseum. The buildings and structures present a living model of life in the Roman capital.

Built in AD 100-110 by Apollodorus of Damascus, an architect who always followed Trajan in his adventures. During the Middle Ages the complex was transformed by adding floor levels still visible today and building defensive elements such as the Torre delle Milizie, built in 1200.

Torre delle Milizie is the tower in the center of the picture and is one of the main mediaeval monuments of the city.Its base sides measure 10.5 x 9.5 m, and it currently stands at almost 50 meters. The earthquake of 1348 caused both the crumbling of an upper floor and the slightly tilting of the structure. In origin it belonged to a series of fortified edifices grouped around a court, in which the tower was located.

At the end of the 13th century the tower was a possession of the powerful Annibaldi family, who were followed by the Prefetti di Vico and by the Caetani, Pope Boniface VIII's family. Under the Caetani the fortified quarter was enlarged and strengthened, probably rivalling with Castel Sant'Angelo as Rome's main fortress. When Henry VII of Luxembourg came to the city for his coronation as Holy Roman Emperor (May-June 1312), he chose the Torre delle Milizie as the base for his Guelph supporters. Twenty years later the tower was ceded to the Conti. During their ownership Raphael, in his role as curator of the antiquities of the city, cited the tower as an example of an edifice built re-using antique parts. The Conti held it until 1619, when it was acquired by the nuns of the neighbouring convent (later demolished) of Santa Caterina a Magnanapoli.