Naga fireballs, Thailand (October) - The great balls of fire shooting across the night sky in Nong Khai Province really do have to be seen to be believed. The balls are a mystery; local people blame them on the mythical Mekong serpent.

Wildebeest migration, East Africa (August) - Rampaging animals disregard border formalities in their millions and charge frantically, trampling everything in their path.

Total eclipse of the sun, Antarctica (13 November) - It will mainly be visible on the least visited side of Antarctica, but a partial eclipse can be seen over most of Australia and New Zealand.

Aurora borealis, northern countries (November to March) - Charged particles from the sun collide with the atmosphere creating an amazing natural light show.

Whale-watching - Various locations throughout the year but try the seas off Kaikoura, New Zealand, for a great variety of sea life and normally reliable sightings.

Flowering desert, Chile - Difficult to predict, but the sudden sprouting of dormant wildflowers is a stunning spectacle. Try the Atacama Desert north of La Serena in September.