南都 ("Southern Capital") is not a single place but a label reused across dynasties. In the Eastern Han, it referred to Nanyang (
南阳, Emperor Guangwu's hometown) — Zhang Heng's famous rhapsody 《
南都赋》 describes that city. In the Ming, after the capital moved north to Beijing, Nanjing was called
南都. The term thus marks wherever the "southern" half of a dual-capital system sat.