It is essentially impossible to define the world’s largest empire – the historical definition of “large” can have various meanings, from population size to geographic extent to level of political control and/or societal consolidation. However, it is possible to determine the world’s largest continuous empire (aka side-by-side, with all territories in physical proximity to each other). This honor belongs to the Mongol Empire, first created under the infamous auspices of Genghis Khan. Beginning with Genghis Khan’s assumption of leadership in 1206, the Mongol Empire continually expanded its borders through warfare, eventually stretching all the way across Eastern Europe to the Sea of Japan and southward across the Indian subcontinent and into modern-day Iran.

Genghis Khan, who ruled the Mongolian Empire from 1206-1227, controlled the largest, 33 million square kilometers, contagious land area in human history. After uniting the many nomadic tribes of northern Asia, he began expansion westward — eventually making it to the European plateau. Widely considered genocidal, he also brought the silk road under one commander and widespread cross-cultural communication across the Asian continent. 

Charlemagne, with the approval and blessing of the Pope, united the majority of Western Europe under a single empire called the Carolingian Empire. After the fall of Rome he was the first ruler to accomplish this task and the lands and boundaries he established laid the groundwork for the modern states of France and Germany. 

After the fall of the Tang dynasty in the early tenth century, China fragmented into several smaller states. The largest of these states was the Song, which ruled over a stretch of China from the Yellow river in the north to the Vietnamese border in the south.

The Jagatai Khanate was one of the four divisions of the Mongol Empire (along with the Ilkhan Empire, the Golden Horde, and the empire of Kublai Khan in China). The Jagatai ruled over a massive swathe of land in Central Asia, including the vital Silk Road trading city of Samarkand.

All of these empires were completely destroyed by the Mongols in the thirteenth century. The Mongols infamously sacked the city of Baghdad, leading to the destruction of the Abbasid Caliphate and the subsequent degradation of this part of the world for centuries. They conquered Song China and established the Yuan dynasty. They dismantled the Khwarazmian Empire and established the Il-Khanate. They also destroyed the Kievan Rus and founded the so-called Golden Horde which ruled Mongol territory in modern-day Russia and Eastern Europe. These are just a few of the empires destroyed by the Mongols.

Francisco Pizarro conquered and colonized the nation now known as Peru (homeland of the Incan people). Cortez conquered the Aztecs of Mexico, and Ponce de Leon and Coronado are associated primarily with the Caribbean. While similar, Columbus was not a true conquistador and allegedly never saw the Incas.

The Sun Never Sets on the British Empire. This phrase refers to the peak of the empire when the colonies were so vast that it was said that no matter the time of day, somewhere in the world the sun was shining on a British colony. 

All of these nations, except for Germany had numerous colonies in the Americas and were largely dependent on their natural and economic resources as a source of wealth. You could have answered this question either by knowing that Germany was not a colonial presence in America or by knowing that all of the other nations listed were such presences.

While the British famously went on to colonize Australia and many of the surrounding islands, they were not the first to discover its existence and relay that information back to Europe. While on a trade expedition to Indonesia Dutch sailor Willem Janszoon was blown off course. It was there he spotted Australia and made landfall. He was promptly attacked by the local aborigines and he returned to Indonesia.