關於馬可．波羅（Marco Polo, 1254－1324）所述「十二男爵」、「三十四省」，中外學者多有關注，疑不能解。結合元初的歷史事實可以證實「十二男爵」、「三十四省」即是對世祖建元故事「內立都省，以總權綱；外設總司，以平庶政」的域外紀錄。「十二男爵」乃世祖朝都省宰相員額的定制；「三十四省」則是指元初外設的多一級行政區劃宣慰司。至於前人所謂《寰宇記》中的前後「十二男爵」，亦非各有所指，本質上皆是宰相的專稱。而波羅所說亦可調度軍隊去必要駐地的「十二男爵」，實指忽必烈時代以中書省臣商量樞密院事或以中書省官兼樞密院官的宰相成員。至若波羅「十二男爵中的一人駐於揚州」的記述，實乃波羅對元初行省官皆以省官出領其事，以宰執行某處省事繫銜的「異域」載述。「蠻子九國」則包含在波羅的三十四省中即江南九省。

Although scholars both in China and abroad have paid considerable attention to the so-called “twelve barons” and “thirty-four provinces” mentioned by Marco Polo (1254-1324), doubts remain concerning their exact nature. By linking historical facts from the early Yuan dynasty, it can be proven that the twelve barons and thirty-four provinces is an administrative institution established by Kublai Khan (r. 1260-1294), as evidenced by “Zhongtong jianyuan zhao” 中統建元詔 (lit. “imperial decree ordering the establishment of the Zhongtong era [the Yuan dynasty]”). More specifically, the twelve barons is a system that set the number of prime ministers of the Central Secretariat; and the thirty-four provinces refer to the Pacification Offices of many first-class administrative divisions in the early Yuan. As for the two different “twelve barons” identified by previous scholars within Marco Polo: The Description of the World, they are essentially identical and likewise designate prime ministers. Moreover, the twelve barons who could dispatch soldiers to stations deemed necessary, as discussed by Marco Polo, are actually prime ministers who participated in negotiations concerning the Bureau of Military Affairs during the reign of Kublai Khan. Looking at one of Marco Polo's accounts on one of the twelve being stationed in Yangzhou, this remark is a “foreign,” namely European, description of the official provincial, known as xingsheng 行省, system, officials of which are no different from the prime ministers of the Central Secretariat in the early Yuan. Finally, the “nine barbarian kingdoms” 蠻子九國 specifically refer to the nine provinces south of the Yangtze River which are a part of the thirty-four provinces.