Final answer:
The rounding of the Cape of Good Hope was not a serious diplomatic mission in the thirteenth century. It took place in the fifteenth century and was led by Vasco da Gama.
Step-by-step explanation:
The thirteenth century saw several serious diplomatic missions, but one that was not a major diplomatic mission during this time was the rounding of the Cape of Good Hope. This journey, which eventually opened up a maritime route to the Indian Ocean, took place in the fifteenth century, during the Age of Exploration. It was Vasco da Gama who successfully sailed around the Cape of Good Hope in 1497, marking a significant milestone in European exploration.