The medieval mosaics in the atrium of San Marco convey illuminations of an early Christian manuscript of which only the charred remains still exist. The manuscript broaches the issue of medieval influence and thus gives a new insight into how the mosaics came into being. The San Marco mosaics, which are linked to early Christian illuminations of the Cotton Genesis, are interesting for two reasons: they saved precious illustrations which would have otherwise been lost, and they are an example of a medieval reception of an early Christian concept. At a conference in 2012, the different positions concerning the illuminations were discussed for the first time, and the essays in this book are concerned with methodical questions that show the complexity of the transformation of antique ideas into medieval concepts.