work paused after the death of Vladimir, but resumed c. 1030 under Iaroslav. Under his reign, the cathedral dedicated to St. Sophia, also known as the cathedral of Hagia Sofia, in which the Metropolitan was to be seated for the following 200 years. Excavations have found that the original plan of the church also prescribed to the inscribed-cross typology (the church has been extensively modified since its construction due to it falling into ruin during Mongol rule). A multitude of domes is also present in the church, although it is not clear its stylistic origins (while wooden churches have complex roof designs, a clear derivation has not been established). Inside the church, several of the medieval Kievan mosaics created by Greek masters survive and show a provincial Byzantine style. The construction of the church itself is a form of stone and brick masonry called opus mixtum, which means alternating rows of stone and flat brick, or plinthos, meaning crushed brick in lime mortar. The exterior was not as ornate as the interior, relying instead on the mass of the building and sported a pink colour, later covered up with white stucco. It is, however, the only structure from this period that mostly maintains its original interior, and thus can be used as an example for the interiors of these early Kievan churches. Meanwhile, in other urban centers across the medieval Rus, masonry church construction also started to appear. As monastery's and urban center's wealth increased, wooden churches started to be replaced by masonry ones. As more churches were constructed, slight modifications were made to the base inscribed cross typology, as well as created a greater emphasis on verticality. Due to the scale of the churches being constructed, interior mosaics and frescos continued being made by imported Byzantine and Greek masters rather than local craftsmen, and thus continued using the Byzantine style. Local contribution to construction, however, meant that modifications were still made, resulting in the Kievan Rus style of ecclesiastical architecture which drew from influences from Bulgaria, Georgia, and Armenia for these modifications to the Byzantine prototype. Many of these churches suffered severe neglect following Mongol invasion, and thus were largely modified in the centuries following. Novgorod Following the conversion of the Kievan Rus to christianity under Vladimir's reign, Bishop Joachim of Kherson commissioned Novgorod's first masonry Church (not extant) as well as the original wooden church of St. Sophia.