Marco Polo is easily one of the best Great Merchants in the game. Additional capacity for Trade Routes in and of itself is powerful, and the free Trader unit saves a lot of Production. The bonus Gold is an added incentive for other civs to trade with the city in which he is activated, so he has great energy with Egypt and the University of Sankore. Other trade-focused civs, such as Portugal and Mali, should also make Marco Polo a priority.
Likely the most famous tourist in history, the peripatetic Marco Polo was born in Venice in 1254 AD to a wealthy merchant family. Since the primary goal of the wealthy seems to be to amass more wealth, young Polo spent most of his childhood being raised by others, since his father and uncle, Niccolo and Maffeo, were off on trading ventures. Having made contact with the court of Kublai Khan, the brothers Polo returned to Venice in 1269. They outfitted a new trading expedition and two years later set off for the Far East again, this time with young Marco in tow.
The Khan had expressed some interest in learning more about Christianity, and the expedition was to have been accompanied by 100 priests at Kublai’s request. But the Polos could only recruit two, and these soon turned back after getting a taste of the rigors of travel. But the rest of the expedition persevered through the harsh conditions and after four years reached Xanadu, the summer palace of the Khan of China. Kublai seems to have liked them, for Niccolo and Maffeo were given important positions in the court while Marco was employed by the Khan as a special envoy to far-flung places such as Burma and Tibet.
But all good things must come to an end, and the Polos headed back to the West, in escort of a Mongolian princess bound for marriage to a Persian prince. The Polos left with a caravan of several hundred; by the time they reached Hormuz in Persia, just 18 – including the bedraggled princess – remained alive. Two years later, Marco returned to Venice, took up the family business, married, raised three daughters, and died peacefully in January 1324 … his tales an inspiration to the adventurous and greedy ever since.