Dating from the beginning of the 9th century, this unusual circular Byzantine-style church was named after the bishop who commissioned it. As one of only a handful of buildings from the early Croatian kingdom to have survived the Mongol invasion of the 13th century, it's a particularly important cultural relic. The simple and unadorned interior includes two complete Roman columns, recycled from the Forum. Also from the Forum are the paving slabs that were revealed after the original floor was removed.

　　The church hasn't been used for services for around 200 years and these days it often serves as a concert hall or exhibition space.