On the east side of the Baptistery, a few feet away from the famous Porta del Paradiso, stand two ancient porphyry columns.
The columns arrived in Florence in 1107, a gift from the city of Pisa, in thanks for the aid Florence had provided in a naval battle against Muslim pirates in the Mediterranean sea.
The two columns were reputed to possess magical properties: it was possible to see, reflected in the polished surface, any future acts of treason against the state. However, the wily Pisans, before handing the columns over to the Florentines, passed them through a furnace, thus destroying their lustre and, consequently, their magical powers.
The columns were once freestanding, as we can see on the panel of a cassone in the Museo del Bargello. Felled by a violent storm in 1429, the columns were hooped and placed in their current position.