The new expanded city, with its splendid buildings in the center measured roughly five kilometers in circumference. The registered population of the Imperial Palace in the center measured roughly five kilometers in circumference. The registered population of Zhongdu amounted to 225,592 households, or approximately one million people.

Mongol armies occupied Zhongdu in 1215. At this time, the city of Kaiping (in present¨Cday Inner Mongolia Autonomous Region) served as the principal Mongol capital (Shangdu), while Yanjing was given provincial status. It was not until 1271 that Kublai Khan formally adopted the new dynasty's name -- Yuan -- and made Yanjing the capital. Kublai Khan rebuilt the city and gave it the Chinese (Han) name of Dadu (Ta-tu) or Great Capital, though in Mongol it was known as Khanbalig (Marco Polo's Cambaluc), the City of the Great Khan. When the Mongols finally eliminated the Southern Song and unified China, Dadu became the political center of the country for the first time in history.
The construction of Dadu began in 1267 and ended in 1293, extending throughout the entire period of Kublai Khan's rule. The magnificent palaces of the Jin capital Zhongdu were destroyed by fire during the dynastic turnover from the Jin to the Yuan. When the capital was rebuilt, the original site of Zhongdu was replaced by a larger rectangular area centered in a beautiful lake region in the northeastern suburbs.
The construction of Dadu consisted of three main projects -- the imperial palaces, the city walls and moats, and the canal. The first stage was construction of the palace buildings, most of which were completed in 1274. The next stage was construction of the mansions for the imperial princes, the government offices, the Taimiao (Imperial Ancestral Temple) and Shejitan (Altar of Land and Grain) to the east and west of the palace, and a system of streets for ordinary residences. In 1293, the strategic Tonghui Canal, connecting the capital to the Grand Canal, was completed.

As the capital city of the Yuan Dynasty (1271-1368), Dadu enjoyed great fame in the 13th century world. The envoys and traders from Europe, Asia and Africa who paid visits to China were astounded by the splendor and magnificence of Dadu. Marco Polo's description of the palaces of Cambaluc, as the called Khanbalig, us most famous of all:
You must know that it is the greatest palace that ever was -- The roof is very lofty, and the walls of the palace are all covered with gold and silver. They are adorned with dragons, beasts and birds, knights and idols, and other such things- The Hall of the Palace is so large that 6,000 people could easily dine there, and it is quite a marvel to see how many rooms there are besides. The building is altogether so vast, so rich and so beautiful, that no man on earth could design anything superior to it. The outside of the roof is all colored with vermilion and yellow and green and blue and other hues, which are fixed with a varnish so fine and exquisite that they shins like crystal, and lend a resplendent luster to the palace as seen for a great way around.
The new Dadu was a rectangular city more than 30 kilometers in circumference. In the later years of Kublai Khan's rule, the city population consisted of 100,000 households or roughly 500,000 people. The layout was the result of uniform planning, the broader streets all 24 paces wide, the narrow lanes half this width. The regular chessboard pattern created an impression of relaxed orderliness.