This kingdom descends on this side towards us, and towards Prussia and Russia. And through that country runs the river Ethille, which is one of the greatest rivers in the world; and it freezes so strongly all year, that many times men have fought upon the ice with great armies, both parties on foot, having quitted their horses for the time; and what on horse and on foot, more than 200,000 persons on every side. And between that river and the great Sea of Ocean, which they call the Maure Sea[401], lie all these kingdoms. And towards the head beneath in that realm is the mountain of Chotaz, which is the highest mountain in the world; and it is between the Maure Sea and the Caspian Sea. There is a very narrow and dangerous passage to go towards India; and therefore king Alexander made there a strong city, which they call Alexandria, to guard the country, that no man should pass without his leave; and now men call that city the Gate of Hell. And the principal city of Comania is called Sarak, which is one of the three ways to go into India; but by this way no great multitude of people can pass unless it be in winter; and that passage men call the Derbent. The other way is from the city of Turkestan, by Persia; and by that way are many days' journey by desert; and the third way is from Comania, by the great sea, and by the kingdom of Abchaz. And you shall understand that all these kingdoms and lands above mentioned, unto Prussia and Russia, are all subject to the great chan of Cathay, and many other countries that border on them. CHAPTER XXV. OF THE EMPEROR OF PERSIA, AND OF THE LAND OF DARKNESS, AND OF OTHER KINGDOMS THAT BELONG TO THE GREAT CHAN OF CATHAY, AND OTHER LANDS OF HIS, UNTO THE SEA OF GREECE.