What role did marco polo serve in the mongol empire?

Marco polo was an administrator for 17 years - 2 Marco Polo was probably born in Italy (some sources also claim Croatia) and travelled together with is older brother to th ecourt of Kublai Khan (the mongol emperor at the time). 
There he served for around 16 or 17 years in different administrative roles for him as he proved very useful for Kublai Khan before returning back to Venice.

Tenochtitlán was the capital of the aztec empire. it was a busy and bustling city where“there are daily more than 60,000 souls, buying and selling, and where are found all the kinds of merchandise produced in these countries.” when cortes arrived in 1519, theenormity of the trading market and the smoothness of it’s running both surprised and  impressed him.