Ha Long Bay is twice recognized by UNESCO. (Photo: BNews/VNA)

The region is a highly diverse area unique in Asia, possessing 7 adjacent tropical and subtropical marine-island ecosystems that developed successively. Ha Long Bay in Quang Ninh province was named by UNESCO as a world heritage site twice in 1994 and 2000.

In 2016, Hai Phong city coordinated with Quang Ninh province to build a dossier that combined Ha Long Bay and Cat Ba Archipelago into a single heritage complex. The dossier was submitted to UNESCO after the Prime Minister’s approval.