Sui Dynasty

State · 587–627 CE · at its largest around 612 CE

In under four decades, the Sui reunited China after centuries of division and dug the Grand Canal linking the Yangtze to the north. They introduced civil service examinations, promoted Buddhism, and laid out the capital that the Tang made into Chang'an.

On its lands while it lasted

Co Loa Citadel (c. 256 BCE – c. 965 CE): Capital of Âu Lac (256 BCE–207 BCE), Ngô Dynasty (947–965).
Goguryeo (c. 37 BCE – c. 668 CE): Kingdom traditionally founded by Jumong in 37 BCE that grew to rule northern Korea and Manchuria.
Bagan (200–1293 CE): Capital of Pagan Kingdom (850–1293).
Sui reunification of China (589 CE): The Sui dynasty conquered the southern Chen dynasty, reuniting China after nearly three centuries of division.
Emperor Taizong of Tang (598 CE – 649 CE): Second Tang emperor, whose reign (626–649) is remembered as a model of good government and military expansion.
Imperial examination system (605–1905 CE): The Sui formalised civil service examinations for selecting officials, a system that lasted until its abolition in 1905.
Zhaozhou Bridge (c. 605 CE): Open-spandrel segmental stone arch bridge designed by Li Chun under the Sui; the world's oldest standing bridge of its type.
Grand Canal (c. 609 CE): The world’s longest artificial waterway. The Sui dynasty joined older canals into a network by about 609 CE; the Yuan realigned it to run directly north to Beijing by 1293, the course it follows between Beijing and Hangzhou today.
Tang dynasty (618–907 CE): The Tang dynasty, ruling from Chang'an, presided over a cosmopolitan golden age of poetry, Buddhism and trade.
Wu Zetian (624 CE – 705 CE): The only woman to rule China as emperor in her own right, proclaiming the Zhou dynasty (690–705) with Luoyang as her capital.