The Romanesque window found in its south facade is the best evidence that the church must have been built as early as the 13th century as is also the semicircular ground-plan of St. Mary's chapel (later altered).

Massive round columns support heavy ribbed vaults cut in stone and an air of peace and sublimity characterizes the church interior in its simplicity.

The most valuable part of St. Mark's Church is its south portal, considered to be the work of sculptors of the Parler family from Prague (end of the 14th century).

On the roof, tiles are laid so that they represent the coat of arms of Zagreb (white castle on red background) and Triune Kingdom of Croatia, Slavonia and Dalmatia.

[6] As the corner of St. Mark's Square and the present day Street of Ćiril and Metod, was a Town Hall, the seat of the city administration in medieval times.