The Tabularium was used for the conservation of the bronze tabulae containing the laws and the official deeds of the Roman State. The building occupies the area of the Asylum, the depression of the Capitoline Hill between the Arx and the Capitolium. The monument is on top of a tall base, its function being defensive and also to raise to the square level of the Asylum the archive. 

A steep staircase inside the basement, access to which was later sealed off on account of its being covered by the podium of the temple of Vespasian and Titus, joined the Forum level to the temple of Veiovis, while a second staircase led to the upper floor of the Tabularium. The narrow corridor on the first floor, illuminated by rectangular openings hewn out of the sturdy basement, is covered by a pavilion-vaulted gallery with large archways framed by architectural features; the gallery can still be visited and is well preserved. 

In the Middle Ages a fortress was built over the remains of the Tabularium, and this was later transformed into the Palazzo Senatorio. Since then, the building has been used for functions associated with the city's administration.