The mosaic floor can be reached through two flights of stairs on the sides of San Columba Basilica’s main chapel; the stairs lead to an ambulatory floor 2,40 m below the upper floor. This prized mosaic floor dating back to the half of the 12th century lies behind the grating.Discovered during some excavations in 1910, it shows Agilulfo’s Basilica real level. Its dimensions are 10 x 10 m. It used to have a dydactic-decorative function, it probably was a kind of carpet upon which the faithful might see biblical scenes and understand the structure of the months of the year. In effect, the figures are all oriented towards the people. The whole composition is divided into two distinct parts: one represents the symbolic fight between good and evil, the other one represents the calendar.