By order of the Florentine scholar Niccolò Niccoli and the cardinal Girodano Orsini, the Florentine Christoforo Buondelmonti visited the Aegean Islands and Creta in the first third of the 15th century, and continued his journey into the Sea of Marmara. He explored the Greek islands and recorded his observations and experiences in letters to Orsini. He set down his insights in two works which are known in different versions: the “Liber insularum archipelagi” and the “Descriptio insulae Cratae”. They are recorded, for example, in a composite manuscript in the university and state library in Düsseldorf (Ms. G 13). The Düsseldorf Version of the “Liber insularum” owes its special importance to its illustrations: the maps of the islands described also show major buildings. The full-page view of Constantinople plays a central role, shedding an entirely new light on the topography and building history of the town in the late 15th century. The text itself gives a detailed description of the cultural, social and economic circumstances in the places Buondelmonti visited. However, as is typical for the age of Renaissance humanism, the text’s main focus is on the search of residues of ancient culture. The edition by Karl Bayer includes a German translation, an overview map, annotations and extensive registers.