Marco Polo's focus when describing Java is evidence of what development from c. 1200 to c. 1450?

It was the rise of the modern age.

Explanation:

Marco Polo witnessed the era of splendor of the Mongol Empire and saw things that his Venetian neighbors could not even dream of: remote cities, huge palaces, unknown religions, and strange animals.

When he returned home, many did not believe the wonders that counted. In fact, some parts of the book are believed to be pure invention, but there is no doubt that Marco Polo was one of the greatest travelers in history.

Curiously, after living so many adventures, his story has reached our days by chance: the one that caused him, when he lost that battle against the Genoese, to end up in a cell with a writer who told his story and made it eternal