It was built using the local stone of Trani, typical of the region: a calcareous tuff, obtained from the caves of the city, characterised by its colour, an extremely light pink, almost white.
The cathedral is distinguished by its showy transept and by its use of the high pointed arch in the passage beneath the bell tower, which is unusual in Romanesque architecture.
The decisive stage of construction probably took place between about 1159 and 1186 under the leadership of Bishop Bertrando II, and the building was complete by about 1200, except for the bell tower, which was only finished in the 14th century.
The main pavement is at some 5 meters above the external ground level, as the nave and the two aisles are built above a crypt corresponding to the original church.
The central bronze door was executed by Barisano da Trani in 1175; the original piece is now inside the church, while the external one is a replica made in 2012.
These include scenes such as the allegory of Alexander the Great flying to heaven (see below) and the original sin episode with Adam and Eve.
A small stairs leads to the hypogeum of St. Leucius, located below the sea level and decorated with frescoes in poor state of preservation.