The park is home to million-year-old limestone mountains. Gradual subsidence has made giant holes which are now habitats for tropical vegetation.

Meanwhile, some other arc-like mountains may give visitors the impression of a gate of heaven.

Travelers are sometimes enchanted by a giant lonesome limestone mass in unique shape in the rice field.

Last but not least, mysterious caves in such limestone mountains always arouse curiosity from adventurers.

The beautiful sky viewed from Ngu Lao Hole - PHOTOS: THU HUONG Mountains are half hidden in white clouds in Cao Bang’s Hoa An Commune A “gate of heaven” in Dam Thuy Commune An explorer poses for a photo in a cave in Ngu Lao limestone mountainous area Stalactites and stalagmites in a big cave in Van Trinh Commune Plants at the entrance of another cave in Van Trinh A lonesome giant limestone mass

Source: Saigon Times