Architecture of Mongolia
The Xiongnu confederation ruled present-day Mongolia from the third century BCE through the first century CE, living in portable, round tents on carts and round yurts. The Xiongnu aristocracy lived in small palaces, and their villages were protected by huge walls. S. I. Rudenko also mentions capital construction built of logs. Archaeological excavations indicate that the Xiongnu had towns; their chief city was Luut Hot (Dragon City).
Zhang Qian
Zhang and Ganfu (as well as Zhang's Xiongnu wife and son) were eventually able to escape and, passing Lop Nor and following the northern edge of the Tarim Basin, around the Kunlun Mountains and through small fortified areas in the middle of oases in what is now Xinjiang until they made their way to Dayuan and eventually to the land of the Yuezhi. The Yuezhi were agricultural people who produced strong horses and many unknown crops including alfalfa for animal fodder. However, the Yuezhi were too settled to desire war against the Xiongnu. Zhang spent a year in Yuezhi and the adjacent Bactrian territory, documenting their cultures, lifestyles and economy, before beginning his return trip to China, this time following the southern edge of the Tarim Basin.
On his return trip he was again captured by the Xiongnu who again spared his life because they valued his sense of duty and composure in the face of death. Two years later the Xiongnu leader died and in the midst of chaos and infighting Zhang Qian escaped. Of the original mission of just over a hundred men, only Zhang Qian and Ganfu managed to return to China.