First king of Kingdom of Croatia, Tomislav from the House of Trpimirović was crowned around year 925 as rex Chroatorum and he united Pannonian Principality and Littoral Croatian Duchy into respectable medieval country which peaked during the reign of Petar Krešimir IV (1058–1074).
Other bigger cities were Zadar, Split, Krk, Osor, Trogir, Ston and Dubrovnik, in which big number of original Roman population resided that was eventually Croaticized.
From this time, there are dozens of large churches, and over a hundred small ones preserved across the Croatian coastline and islands.
They are all built out of roughly broken stones covered with thick layer of moulter inside and out, and with narrow decorative niches with arched top (like church of st. Peter in Priko near Omiš and St. Michael near Ston).
The church was of unified Croatian pre-Romanesque forms and those Romanesque that appeared with the arrival of Benedictine monks in these parts.
When the bishopric was founded in Zagreb (1090), Croatian culture at the coast has already flourished for 300 years and Croatia was at the end of its independence.
That inscription of king Zvonimir is already made in Croatian, written in Glagolitic script (Baška tablet).
Sheer number, but also the quality of stonework, of these monuments tells us of rich masonry tradition of numerous masters and workshops on the east coast of Adriatic.
In Zagreb there is a Liber psalmorum which was illuminated in Benedictine style by prior Majon for archbishop Paul of Split (c. 1015–1030).
In Vatican there is a Breviary, also in monte-cassino Benedictine style (initials of intertwined leaves, interlace and animal heads) which originates from monastery of St. Nicola in Osor.
The same style of illumination we can found in Breviars in Trogir, Šibenik and Dubrovnik but there are many that were recorded (like 47 books in only one church in monastery of St. Peter in Seka) but not preserved.