Phong Nha
Phong Nha was the highlight of my trip. It is known for its caves and the Phong Nha-Kẻ Bàng National Park which is a Unesco World Heritage site.It is home to over 300 caves and grottos. In 2009 the Hang Sơn...
...Đoòng cave was discovered and thought to be the largest in the world. See https://en.wikipedia.org/wiki/Hang_S%C6%A1n_%C4%90o%C3%B2ng