The Krk cathedral carries the name of the Blessed Virgin Mary, which according to the discovered inscription about the construction, probably existed in the second half of the 5th and the beginning of the 6th century, so its name is connected with the Council of Ephesus (431) and the great celebration regarding the acknowledgement of Mary as the Mother of God. Until today the Romanesque edifice has remained preserved with its extremely rich inventory, and small additional constructions from the later period of Gothic, Renaissance and Baroque stylistic features.

The archaeological findings prove the existence of the original antique layer, the thermae from the 1st century, at the site of today’s cathedral.

Considerable reconstruction was undertaken in the Romanesque period on the entire cathedral complex. The inscription on the cathedral mentions the reconstruction of the colonnade (columnarum opus) in the 12th century, conducted by the unknown Krk bishop (mentioned by the initial D), but it most probably happened during the time of the bishop Dabar (Dobro – Bonus) around 1179. A part of the cathedral complex today constitutes the church of St Quirin, a beautiful example of the Romanesque sacral architecture. The first information about it dates back from 1335 when the people of Krk gave the rent from the island Plavnik “for the repair of the church of St Quirin in Krk”. It is assumed that it was built in the 12th century. The church is particular for its two floors and its geographic orientation as its apse is completely untypically directed towards the south, probably owing to the constricted space on which it was built. The upper church is dedicated to St Quirin, the patron saint of the city of Krk, and the lower church of St Margaret was dedicated to the martyr from Antiochia. These Romanesque churches were built from white local stone. The appearance of the church is complemented by the three-apse ending with prominent ornament of blind Romanesque arcades at the top and the border made of polished red local stone (mandorlat) in the middle.

It is assumed that the upper church (St Quirin) was actually the matroneum of the cathedral from where the women used to participate in the mass held in the cathedral. There is a possibility that St Quirin had the function of a palatine chapel of the Krk bishop or a western edifice (gallery, westwerk) from where the Krk princes followed the mass.

The bell tower of the Krk cathedral is situated at the northern façade of St Quirin. The place of its construction was determined by the Venetian provveditore Vinciguerra in 1489, while the construction was finished in 1515. The bell tower was hit by lightning in 1714, when the main keystone pyramid cracked and crashed.

In the 1760s, a thorough restoration was undertaken according to the sketches by the Venetian architect Pietro Checchi. A wooden angel coated in copper plates, made in Venice, was placed on the bell tower. Since 1973, there is a plastic angel at the top of the bell tower made according to the mould of the decrepit old angel.