This essay was carried out in the framework of a research programme (Thesaurus Mediaevalis, Eötvös Loránd University, Budapest, 2017–2022) funded by the Hungarian Academy of Sciences, and deals with one of the most complex but hardly accessible works of the Árpád period, the former main portal of the Esztergom Cathedral, which was decorated with sculptures and inlaid marble images. It was built in the last decade of the 12th century under King Béla III (1172–1196) and survived the Turkish invasion, but its remains were destroyed during the 19th century construction works. Since then, it exists only in textual sources, depictions and museum fragments. The present work aims primarily to collect and catalogue the fragments, but also to examine the structure of this work of exceptional quality, the artistic orientation of its workshop and the content of the images. It examines questions such as the history of the construction of the building, the sculptural quality of the fragments, which European art centres are related to them (including, in addition to the dominant role of the centres in northern Italy, the Byzantine influence conveyed by the various forms of transport), the circumstances under which the artists could have arrived in the Kingdom of Hungary, the inspiration for their art, what their knowledge and the needs of their clients reveal, and whether there were any interruptions, changes of plan or new beginnings during the construction.