Definitions for "Guanzhong"
Guanzhong (關中) historically refers to an area that was bound by Hangu Pass to the east, Dasan Pass (大散關) to the west, Wu Pass (武關) to the south, and Xiao Pass (蕭關) to the north -- modern central Shaanxi and extremely western Henan. It formed the center of Qin during the Warring States period, and had fertile soil and good irrigation systems that helped Qin's rise among the warring states to eventually unite them into Qin Dynasty. It also served as the capital region for Han Dynasty, Sui Dynasty, and Tang Dynasty.