In 442, at Kou Qianzhi's urging, Emperor Taiwu ascended a platform and formally received Taoist amulets from Kou, and changed the color of his flags to blue, to show his Taoist beliefs and to officially approve Taoism as the state religion. From that point on, it became a tradition for Northern Wei emperors, when they took the throne, to receive Taoist amulets. Also at Kou and Cui Hao's urging, he started building Jinglun Palace (靜輪宮), intended to be so high that it would be quiet and close to the gods. (Emperor Taiwu's crown prince Tuoba Huang, a Buddhist, opposed the construction project on the basis of cost, but Emperor Taiwu disagreed with him. This might be the first sign of growing tensions between Cui and the crown prince.)