If someone asked you 'who was the richest man ever?' your answer would probably be Bill Gates, Jack Ma, Jeff Bezos, or maybe John Rockefeller.
The correct answer is much more unexpected The richest man to ever walk the face of the Earth is Musa Keita, Malian emperor, and this is story about him.

Your first question is probably 'how rich he was?'. The answer is- richer than anyone can describe. Without exaggeration, his fortune was incomprehensible. Some assumption is that he was worth 400 billion dollars, in today's money. That is five times more than Bill Gates, for example.

Your next question is 'who was this guy, and how did he become so rich?'.
Musa was emperor of Mali (1280-1337) and he is usually known as Mansa Musa (Mansa means king).
When he came to the throne, his kingdom consisted of today's teritorries ogf Ghana, southern Mauritania and Mali. But during his rule, Mansa Musa expanded the borders of his kingdom tremendously. To put in today's perspective he ruled the land of today's countries of Guinea, Senegal, Nigeria, Chad, Mauritania, Gambia, Burkina Faso, Niger and Mali. The land was rich in salt and gold and Mansa Musa exploited those resources to the maximum.

Just not to forget, during the time of his reign, much of Europe was in civil wars.

Travel to Mecca

Mansa Musa was devoted Muslim. In 1324 he went on a 4000 mile long trip to Mecca, and he did everything to show how rich he was. He brought a caravan with himself, stretching as far as eye could see. He was accompanied by 40000 soldiers, civilians and 12000 slaves and 500 heralds bearing gold stuffs, and many camels and horses.
On his stop in Cairo, he spent and donated so much gold, that he caused mass inflation, because sudden influx of gold devalued the metal for the next decade. It would take years for city to fully recover from this crisis.

Education

He took a particular interest in the city of Timbuktu. He urbanized city by building schools, mosques and a university.

He brought architects from Andalusia to build his grand palace in Timbuktu and Djinguereber mosque, which still stands, and is one of the main attractions in Timbuktu today. Picture of Djinguereber is below.

Soon, Timbuktu became center of African trade, culture and Islam, It even attracted merchants from Venice, Genoa and Granada.

Mansa Musa was succeeded by his son, however his heirs were unable to hang on to the fortune, and it was substantially depleted by civil wars and invading armies.