The cathedral was consecrated in 1075 and has a columned portico in front. It stands on a pretty square, which has preserved the flagstones of the old Roman forum. The campanile with small columns is from the Romanesque-Gothic transition period. Inside, the 13C pulpit and paschal candelabrum are fine works by the Cosmati (a guild of marble masons specialising in assembling fragments of multi-coloured marble and inlaying pieces of enamel on the small columns and friezes of cloisters).