The imperial city of Cambalu, the modern Peking, formed the residence of the khan during the months of December, January, and February. The palace of Kublai stood in the midst of a prodigious park, thirty-two miles in circumference, surrounded by a lofty wall and deep ditch. This enclosure, like all Mongol works of the kind, was square, and each of its four sides was pierced by but one gate, so that between gate and gate there was a distance of eight miles. Within this vast square stood another, twenty-four miles in circumference, the walls being equidistant from those of the outer square, and pierced on the northern and southern sides by three gates, of which the centre one, loftier and more magnificent than the rest, was reserved for the khan alone. At the four corners, and in the centre of each face of the inner square, were superb and spacious buildings, which were royal arsenals for containing the implements and machinery of war, such as horse-trappings, long and crossbows and arrows, helmets, cuirasses, leather armour, &c. Marco Polo makes no mention of artillery or of firearms of any kind, from which it may be fairly inferred that the use of gunpowder, notwithstanding the vain pretensions of the modern Chinese, was unknown to their ancestors of the thirteenth century; for it is inconceivable that so intelligent and observant a traveller as Marco Polo should have omitted all mention of so stupendous an invention, had it in his age been known either to the Chinese or their conquerors. Indeed, though certainly superior in civilization and the arts of life to the nations of Europe, they appear to have been altogether inferior in the science of destruction; for when Sian-fu had for three years checked the arms of Kublai Khan in his conquest of Southern China, the Tartars were compelled to have recourse to the ingenuity of Nicolo and Maffio Polo, who, constructing immense catapults capable of casting stones of three hundred pounds’ weight, enabled them, by battering down the houses and shaking the walls as with an earthquake, to terrify the inhabitants into submission.