The Taiga forest, on the edge of the Arctic, is a silent world of stunted conifers. The trees may be small but filming from the air reveals its true scale. A third of all trees on Earth grow here and during the short summer they produce enough oxygen to change the atmosphere. In California General Sherman, a giant sequoia, is the largest living thing on the planet, ten times the size of a blue whale. The oldest organisms alive are bristlecone pines. At more than 4,000 years old they pre-date the pyramids. But the baobab forests of Madagascar are perhaps the strangest of all.

Life goes to extraordinary lengths to survive this immense realm. A 30 tonne whale shark gorges on a school of fish and the unique overhead heli-gimbal camera reveals common dolphins rocketing at more than 30km an hour. Descending into the abyss, deep sea octopus fly with wings and vampire squid use bioluminescence to create an extraordinary colour display. The first ever time-lapse footage taken from 2,000m down captures eels, crabs and giant isopods eating a carcass, completely consuming it within three hours.

Intrepid adventurer Michael Palin travels through Pakistan's North-West Frontier Province, starting on the Khyber Pass and ending five miles from K2 on the Pakistan/China border. He passes through Darra, visits a street dentist in Peshawar, goes bull racing with a Pakistani aristocrat and is almost trampled to death, and finally crosses over the Lowari Pass into the buffer state of Chitral.

Julian Richards investigates the impact of the Vikings in Britain. This edition focuses on the archaeological trail left by the Vikings as they travelled from Norway along the sea road to Dublin. Settlements, a boat burial and evidence of trading have been discovered on the Scottish isles, and silver hoards found in Ireland suggest that Dublin was not only wealthy and important, but also a centre for trade in slaves.

The Queen of Sheba - an exotic and mysterious woman of power - is immortalised in the world's great religious works, among them the Hebrew Bible and the Muslim Koran. She also appears in Turkish and Persian painting, in Kabbalistic treatises, and in medieval Christian mystical works, where she is viewed as the embodiment of Divine Wisdom and a foreteller of the cult of the Holy Cross. In Africa and Arabia her tale is still told to this day and, indeed, her tale has been told and retold in many lands for nearly 3,000 years.

Our journey begins with David Attenborough at the North Pole, as the sun returns after six months of darkness. We follow a pair of courting polar bears, which reveal a surprisingly tender side. Next stop is the giant Greenland ice cap, where waterfalls plunge into the heart of the ice and a colossal iceberg carves into the sea. Humpback whales join the largest gathering of seabirds on earth to feast in rich Alaskan waters. Further south, the tree line marks the start of the Taiga forest, containing one third of all trees on earth. Here, 25 of the world's largest wolves take on formidable bison prey. At the other end of our planet, the Antarctic begins in the Southern Ocean where surfing penguins struggle to escape a hungry sea-lion and teams of orcas create giant waves to wash seals from ice floes -a filming first. Diving below the ice, we discover prehistoric giants, including terrifying sea spiders and woodlice the size of dinner plates. Above ground, crystal caverns ring the summit of Erebus, the most southerly volcano on earth. From here we retrace the routes of early explorers across the formidable Antarctic ice-cap - the largest expanse of ice on our planet. Finally, we rejoin David at the South Pole, exactly one hundred years after Amundsen then Scott were the first humans to stand there