给定一段中文文字，请将其翻译成英文。
汉朝时期，从长安到天山南路，共需要经过两座大山。第一座大山是秦岭，高约四千米。第二座大山便是天山，高二万五千英尺，这座山脉是丝绸之路的重要组成部分。
During the Han Dynasty, to travel from Chang'an to the southern route of the Tianshan Mountains, one needed to pass through two large mountains. The first mountain is the Qinling Mountains, which is about 4,000 meters high. The second mountain is the Tianshan Mountains, which is 25,000 feet high and is an important part of the Silk Road.