The opera Diocletian, in four acts and nine scenes, composed in 1964 to a libretto by Branko Radica, is a monumental and still unperformed musical-theatrical work that depicts the life of the Roman emperor Diocletian. Tijardović's historical spectacle will faithfully bring Diocletian to life in the intimate circle of his family and co-rulers. Written in the style of French classical opera, the opera revives the historical and legendary foundations of the city of Split through a rich spectrum of dramatic and emotional situations: from political intrigues to family conflicts.

The first three acts of the performance are staged inside the building of the Croatian National Theatre Split, while the final, fourth act takes place at the Peristyle.