This is an attempt to present a status quaestionis tracing the parallel development of archeological evidence and its interpretation: 1) at the beginning of this century, the discovery of the problem (Niemann, Gnirs. Egger) following the excavations at Aquileia, Salona and Hemmaberg; - 2) R. Krautheimer's first theory (1936) regarding the case of Pavia, mainly based on mediaeval tradition and liturgical texts from Northern Italy; 3) the extension of those problematics to early mediaeval France (J. Hubert) and mediaeval Russia (A. Grabar (1938-1943); — 4) the excavations at Milano as interpreted by A. Capitano d'Arzago, and the diggings at Trier following the cathedral's bombing during WW II; - 5) the emergence of a general reflection among early mediaevalist circles and J. Hubert's first synthesis (1951); the renewal of researches at Aquileia (M. Mirabella Roberti, G. C. Menis, P.-L. Zovatto et L. Bertacchi) and in the Adriatic area; - 6) the German school's interest in double churches in relation to chur...