1. Genghis Khan
Probably not the first person who springs to mind when you think about an all-time rich-list, but the fearsome Mongol warlord Genghis Khan is the richest person in history by quite a large margin. Between 1206 and 1227, Khan conquered a staggering 12 million square miles of land - the largest contiguous empire in history. The Mongol army pillaged its way through huge swathes of Eurasia (modern-day Europe and Asia) and in doing so claimed spoils of monumental proportions - $100's trillions in today's money, almost impossible to comprehend. Unlike some of his fellow billionaires and trillionaires, however, Genghis Khan didn't hoard his entire endowment. Instead, he spread the wealth and territory among his trusted subjects.
2. Emperor Shenzong of Song
Ruling China between 1067 and 1085 during the 'peaceful prosperity' and 'primary abundance' years, Shenzong controlled almost a third of the world's GDP; more than $30 trillion today. Like King Solomon, Shenzong was particularly adept at collecting taxes. However, philanthropy was also at the heart of the emperor's rule - his administration's 'New Policies' helped improve the lives of the poor, and Shenzong is often credited as pioneering the concept of a welfare state.
3. Akbar the Great
The Indian emperor was named after his ability to bring an enormous amount of wealth to India, and himself in the process. Akbar conquered hundreds of thousands of square miles of territory across the Indian subcontinent, using the riches he won to fund a lavish lifestyle and invest in the arts. Akbar's Mughal Empire controlled approximately 25% of the world's GDP, translating to an eye-watering $21 trillion in today's money.
4. Augustus Caesar
Augustus was the first Roman emperor, ruled over his vast kingdom for an impressive 41 years. During this time, the emperor managed to build a fortune equivalent to 20% of the empire's entire economy to add to the already considerable estate he inherited from Julius Ceasar. In today's money? Just shy of $5 trillion. To put things in perspective, Augustus was so rich he even owned Egypt at one stage.
5. King Solomon of Israel
The Bible tells us that King Solomon of Israel ruled from 970 BC to 931 BC, during which he's said to have received 25 tonnes of gold in taxes for each year of his 39-year reign. That's a lot of gold, worth billions of dollars in today's money. As legend has it, Solomon also extracted hundreds of tonnes worth of gold from his famed mines - where he was also said to store huge amounts of his fortune. Taxes and mining aside, King Solomon also amassed incredible wealth from trade, putting him in the $2 trillion-plus bracket.