 Complete the following phrase:  He left his native city around 1414 CE in order to travel, mainly in the Aegean Islands. He visited Constantinople in the 1420s. He is the author of two historical-geographic works: the Descriptio insulae Cretae 1417, in collaboration with Niccolò Niccoli and the Liber insularum Archipelagi 1420. These two books are a combination of geographical information and contemporary charts and sailing directions. The last one contains the oldest surviving map of Constantinople, and the only one which antedates the Ottoman 