Luoyang, the eastern capital, is the cosmic capital of the Tang Dynasty. In 657, Tang Gaozong issued the Imperial edict on East Capital, claiming that East Capital is a "Sino-Swiss Universe" and all of them live in various countries. Dongdu, today's Luoyang, is the central city of the Grand Canal in Sui and Tang Dynasties. After Tang Gaozong moved to Luoyang, Chang 'an became the capital.

When Wu Zetian proclaimed himself emperor, he also took Luoyang as his capital and named it Tangxi, Tongzhi Ji Jian. Luoyang also established the Shu Tian, the symbol of the world center, so it really became the capital of the universe.