The remains of The Church Our Lady of Zvonik, located over a cavity of the west wall above the Porta Aurea of Diocletian's Palace.

On 4 March 852 Trpimir issued a charter in Biaći (in loco Byaci dicitur) in the Latin language, confirming Mislav's donations to the Archbishopric in Split.

From the same period are fragments of an altar partition with an inscription mentioning the city prior to Furmin (Firmina) and his first and second wives, Magi and Bitu, as donors.

[5] During the church's remodelling, a small part of an early Romanesque altarpiece was unearthed and reinstalled as an internal frame of a Gothic window.

Firmin and his wives also wear aristocratic insignia (dominus and domina), which means that they are members of the class that, after the collapse of Byzantine rule, fought for independent power in coastal cities, as was the case in Zadar and Trogir.

In 2018, work began on the interior of the Church of Our Lady of the Bell Tower as part of the renovation project of the Iron Gate.

Today what remains is the 11th-century early Romanesque bell tower (dated in terms of construction and stylistic features), that once stood above the central transept.

It has a slender but closed wall mass, on which, in addition to small windows, one before stands out on each side of the upper floor, representing a transitional form between pre-Romanesque and Romanesque.