The country of the Medes, Herodotus tells us, is very high and mountainous in the north towards the Euxine, and covered with forests, but the remainder of it is flat.[447] Polybius gives a more minute description of the nature of Media. "It is difficult to speak adequately of the natural strength and of the extent of the country of the Medes. It lies in the centre of Asia, and in the size and elevation of the land surpasses all other parts, while the situation enables it to govern the strongest and most populous nations. Towards the east it is protected by the desert which lies between Persia and Parthia, it has control of the Caspian gates, and abuts on the mountains of the Tapurians, which are not far distant from the Hyrcanian Sea. Towards the north it is bounded by the Matieni and Cadusians, on the west it extends to the Saspeires, who dwell close to the tribes which lie on the Euxine. Towards the south it extends to Mesopotamia and abuts on Persia; on this side it is protected by the range of the Zagrus, which reaches an elevation of one hundred stadia, and is broken into various ranges and groups, separated by deep valleys and open plains, in which dwell the Carchi, Cossaei, and other warlike tribes. Media itself is traversed by several ranges in the direction from east to west, but between them are plains filled with cities and villages. The Medes possess corn and cattle in untold abundance, and in horses their country is superior to the whole of Asia, so that it takes the first place, not only in virtue of its extent, but also owing to the number and excellence of the men and horses."[448] Strabo allows Media an extent of 4000 stades (500 miles) in length and breadth. It reached from the Zagrus to the Caspian gates. The greater part of the land was high and cold, but the district below the Caspian gates on the lower ground was very fertile. Even in the rest of the land, with the exception of some mountain districts, there was no lack of the means of subsistence, and everywhere on the high ground there was excellent pasture for horses.[449]