The North and South polar regions of the Earth; the Arctic and Antarctic are the greatest and least known wildernesses.

Spring in the polar regions; the greatest seasonal transformation of the planet begins with the return of the sun.

It is high summer in the polar regions, and the sun never sets; many species take advantage of the easier conditions, but summer is a tough time for the polar bear family, as their ice world melts away and the cubs take their first swimming lesson.

Polar landscapes in autumn are transformed as the big freeze returns; in the Arctic, polar bears gather in large numbers on the coast to wait for the return of the ice; off the coast 2,000 beluga whales head for a special estuary.

Winter is the greatest test for life in the polar regions; in the Arctic, a female polar bear treks into the mountains to give birth; out on the frozen ocean, the entire population of the world's spectacled eider ducks braves the winter.

A look at the extraordinary riches and wonders of the polar regions and the people that have been visiting them for thousands of years.