Cat Ba National Park: This Park had been told covers an area of 15,200 ha, including 9,800 ha of forests with splendid grottoes (cave).

Ha Long Bay has an area of around 1,553km2, including 1,960 islets, most of which are limestone. The core of the bay has an area of 334km2 with a high density of 775 islets. The limestone in this bay has gone through 500 million years of formation in different conditions and environments. The evolution of the karst in this bay has taken 20 million years under the impact of the tropical wet climate (Wikipedia).