An amazing UNESCO cover from Vietnam, depicting a complete set issued in 2017 celebrating the Imperial Citadel of Thang Long - Hanoi.
The Thang Long Imperial Citadel was built in the 11th century by the Ly Viet Dynasty, marking the Independence of the Dai Viet. It was constructed on the remains of a chinese fortress dating from the 7th century and it was the centre of regional political power for almost 13 centuries without interruption. It's inscribed as a UNESCO site since 2010.