Once a year, the French city of Lyon undergoes a giddying transformation, as countless beams of light flicker across the city, bathing its buildings in a tapestry of luminous colours.

The scenery seems to whirl around like a carousel as the visual trickery produces strange effects: A theatre appears to be devouring its audience while, close by, the giant head of a woman pours forth from a fountain.

These are no hallucinations brought on by delirium or scenes from a bizarre 3D animation film.

The event is the Fete des Lumieres, an extraordinary festival of lights in the historic capital of western France. From December 8-11 the metropolis on the river Rhone celebrates itself with a superlative light show driven by the latest technology.

Every year there are around 70 pulsating audio-visual installations to admire during the four days of activities, during which the city is a focal point for lighting wizards and event specialists.

The illuminations have their origin in a thanksgiving celebration to mark the end of a severe plague epidemic more than 300 years ago. The candles of yore have given way to an interactive spectacle which, quite literally, puts most conventional light shows in the shade.