Podul, the fourth tropical storm to hit Vietnam this year, weakened into a tropical depression after making landfall around 1 a.m. on Friday in the central provinces of Ha Tinh and Quang Binh with wind speeds of 60-75 kph.
To ensure the safety for visitors, Quang Binh authorities have asked all tourist destinations, including Phong Nha-Ke Bang National Park and Tu Lan Cave System, to stop receiving visitors.
Accommodation facilities must have plans to ensure safety for visitors as well as provide adequate food during their stay. Travel agencies are not allowed to organize sightseeing tours as the province is being hit by heavy downpours.
The management board of Thien Duong (Paradise) Cave, recognized as having "the most unique and magnificent system of stalactites and stalagmites" in Asia by the Asia Book of Records, has stopped receiving visitors from Friday and has not announced when it will reopen.
Established in 2000, Phong Nha-Ke Bang is frequently referred to as the "Kingdom of Caves" for the magnificent specimens it hosts.
The 900-square-kilometer national park, which UNESCO recognized as a global heritage site in 2003, is home to over 300 caves and grottoes that date back some 400 million years.
Around 30 caves are now open to visitors, which has created a tourism boom and given much-needed revenue to the once war-torn province.
Last year, Quang Binh welcomed a record-breaking 3.9 million tourist arrivals, up 18 percent year-on-year.
A video captures the beauty of Tu Lan Cave, a popular adventure destination in Quang Binh Province.