The annual performance - staged along a 5 km (3 mile) path inside the cave - has become one of Slovenia's top tourist attractions.

"It is definitely a special feeling to sing in what is essentially a natural cathedral, created by nature, the acoustics of the space are entirely different," said Slovenian opera singer Irena Yebuah Tiran who is performing in the spectacle this year.

The tradition of living nativity scenes started in 1989 and features costumed performers, actors and singers amid light and sound effects.

This year 150 performers are acting out the Biblical story of Christmas in 16 scenes set along the path.

The nativity scenes will be open to the general public for six days, starting on December 25, and organisers expect some 17,000 visitors from all over the world to come and enjoy the unique spectacle.

The cave itself was formed over millions of years and becamse well know and a tourist spot in the early 19th century, later to be served by an underground train.

Grafitti on some of the walls, however, are said to date as far back as the 13th century.