The columns of San Lorenzo are an ancient building from the late Roman era in Milan, located in front of the basilica of the same name near the medieval Porta Ticinese. They represent one of the rare surviving finds of imperial Milan.
These are sixteen columns, about 7 and a half meters high, in Musso marble, with Corinthian capitals that support the entablature. In reality, looking closely, there are 17 columns, in fact on the top of the arch which is located in the center of the columns, which differentiates 8 on one side and 8 on the other, there is a miniature column with the cross above it. They come from Roman buildings dating back to the 2nd or 3rd century, probably a pagan temple located in the area of what is now Piazza Santa Maria Beltrade .
The columns were transported to their current location to complete the basilica of San Lorenzo being erected. The capitals instead come from two different buildings; they are in fact different in style and size. A brick shim was added to the lower capitals to level them with the others. The assembly that can be seen today was built in the Middle Ages, between the 11th and 12th centuries, to which the brick parts that complete the architrave date back, with the arch surmounted by the cross in the center of the colonnade. Leaning against the basilica are other bodies, among which the chapel of Sant'Aquilino is noteworthy with mosaics from the Roman age.
Until 1935, in the current square that stands between the Columns and the Basilica of San Lorenzo there was an entire block made up of old popular buildings; this complex was demolished to give, in line with the urban planning principles and guidelines of the time, greater breadth and monumentality to the basilica. The new square was subsequently occupied by the tram tracks, which in the nineties was moved beyond the Colonne, on interpenetrating tracks. From 1937 is the bronze statue of Emperor Constantine, bound to Milan for the promulgation of the famous edict of the year 313, a modern copy of a late antique original preserved in Rome.