Definition of loo-dwin

The term loo or loo-dwin (twisted holes) is applied to natural caves or deep fissures of the karst topography of Mogok. The entrance to these caves is usually indicated by pronounced marble outcrops. These fissures vary in width, length, and orientation, branching out in unpredictable configurations, often several kilometers in length, frequently leading to huge caverns. A cavern may be 10 meters or more at its base, often exceeding 8 meters in height.

Ref: Ted Themelis (2008) Gems & mines of Mogok