The basilica has been preserved up to the roof level. It is the only preserved
sacral building of this type not only on the island of Krk, but on the entire
Croatian Littoral.
The construction of this church on the remains of the Roman town of Fulfinum
marked the beginning of a new Christian town. However, its secrets are yet to
be discovered by experts. Local tradition associates this church with the Glagolitic
Benedictine abbey of St Nicholas, which was abandoned in the 15th
century and relocated closer to Omišalj.
In its original construction phase, this impressive single-nave church had
an entrance area in the front (called the narthex or vestibule), a porch on its
south side, and two smaller side rooms which could be defined as early examples
of a sacristy and which were connected to the wall of the presbytery. The presbytery
itself has a simple layout: its rear is flat and features a freestanding bench
for the clergy. In front of the bench there is part of the presbytery enclosed with
an altar balustrade with a cross-shaped altar tomb at its centre. The entrance area
contains a sarcophagus dug into solid rock and covered with mortar. A privileged
tomb with two deceased was later placed alongside the sarcophagus. It has been dated
to the period between the 7th and 8th century.
The atrium at the south porch, which also features several privileged
tombs, was probably added at the same time. Over the centuries that followed,
this community developed into a well-organised religious community that eventually
took on the teachings of St. Benedictine, as suggested by later sources that mention
the Abbey of St. Nicholas at the foot of Omišalj. Inside this monastery complex,
on the eastern side of the church which also underwent changes in its interior,
there are smaller spaces of a memorial and commercial character.