In this final episode we complete our journey, travelling back from the March equinox to the end of June. Kate Humble is in the Arctic at a place where spring arrives with a bang, whilst Helen Czerski chases a tornado to show how the earth's angle of tilt creates the most extreme weather on earth.

Monty Don embarks on a journey across Spain, discovering gardens across the country’s diverse landscape and exploring its rich and varied history and culture. He will cover more than 4,000 kilometres to visit some of its most interesting gardens, community projects and parks in order to get under the skin of the country. His trips range from historic imperial palaces to cutting-edge modern gardens created by a new wave of Spanish designers working more closely with the landscape and the challenges of the climate.
“Spain's history and its landscapes, climates and cultures have huge diversity. And in this series, I want to get under the skin of the country by visiting as many gardens in Spain as I can so I can shed light on this nation's past, its future and its people. The result is a picture not just of its gardens but this fascinating country itself. Dramatic, proud, complex, but always compelling.”

'Mormon Lost Boys' Young men have been thrown out of their homes because of an edict allowing polygamist church elders to monopolize young girls. 'The Fat Farms of Mauritania' In the West African country of Mauritania, parents send their daughters to rural fattening camps. 'Mumbai Slumscraper' A visit to Mumbai, where slums sit below billion-dollar, single-family skyscrapers.

The Namib Desert is one of the oldest deserts and also one of the most diverse. With 50ºC (120ºF) temperatures and half a millimetre of rainfall annually, we see how this is possible. Half the size of Oklahoma, from its Skeleton Coast through the sea of sand to the haze of distant mountains this apparently forbidding desert hides secret water sources.

A visit to arguably the most famous archipelago on Earth, the Galapagos. It's home to a myriad of bizarre and unique creatures, endemic to these islands - but how did they get here and what is the key to these extraordinary islands that allows them to thrive? The programme reveals that this key holds not just the secret to life here, but also to how Darwin was able to leave with the ideas that would revolutionise biology.

The episode opens with Ewan McGregor and Charley Boorman riding through the sleek streets of Guanacaste, Costa Rica. To add to the excitement, the show also introduces us to Ewan's daughter, Jamyan, and the father-daughter duo are lovable to watch. The audience also gets a chance to see the Masaya volcano up close. The red lava is breathtaking and scary at the same time.