What is the theme in The Travels of Marco Polo by Marco Polo?

Superstition is a central theme. Throughout the empire that Marco Polo travels and explores on behalf of the Great Khan he finds superstitious habits, customs and beliefs practiced by the inhabitants. Many of the beliefs originate in apparent miraculous events that cannot be readily explained by any tenets of natural science that are evident in the thirteenth century. For example, the country of Georgia has a monastery named St. Leonard that claims to have a miraculous lake on its grounds. Fish appear in the lake at the beginning of Lent and remain present during all of Lent until Easter when they disappear. The residents claim this is a miracle, presumably because it coincides with the Church rules of abstinence from eating meat by substituting fish during Lent that become miraculously available.