The Vietnamese word "hang động" refers to a "grotto" or "cave." It is a natural underground space, often formed by geological processes, where you can find interesting rock formations, sometimes with water, and it is typically dark inside.
Basic Use: "Chúng ta sẽ đi tham quan hang động hôm nay."
(We will go to visit the cave today.)
In Context: "Hang động Phong Nha là một trong những hang động lớn nhất ở Việt Nam."
(Phong Nha Cave is one of the largest caves in Vietnam.)