The C4th Roman Rotunda church in Thessaloniki is the most important monument of the early Christian era. In this comprehensive monograph, Hjalmar Torp presents the findings of his life-long archaeological and iconographic research on the Rotunda. He explores the archaeological data, the various phases of the architecture, and the chronological issues of the monument. The nuanced descriptions of the mosaics, their colours and their techniques are based on a detailed scaffold review and survey. The iconography of the mosaics is then analyzed and interpreted in conjunction with historical and theological sources; the building of the palatine church and its sumptuous decoration is attributed to an initiative by Theodosius the Great. This slip-cased set of two books, abundantly documented and richly illustrated, is a unique testimony on the Rotunda. Volume One: text. Volume Two: Illustrations. 500 illustrations, many in colour. This book is only available in French.