Plava Spilja is one of the most beautiful and largest caves in the row of caves in the rock walls, which are located along the very dilapidated banks of the Lustica peninsula in the Boka Kotorska bay. The cave lies between the port of Zlatni harbor and the Cape Mokra Gora, and is located 5.7 nautical miles from Herceg Novi. It has two entrances at a 45-degree angle, a smaller opening on the south side and a larger one on the south-west side, which is 3 meters high and about 15 meters wide. So that ordinary boats and smaller boats can enter the cave.
The depth of the sea within the cave is 4 to 5 meters. The height from sea level to the top of the ceiling is 9 meters and the surface is about 300 m². It got its name due to an unusual crystal blue color that is generated by the reflection of the sunbeams that settle off the surface during the afternoon.