The Tropic of Capricorn runs around the southern hemisphere for about 22,835 miles, crossing some of the most remote and unexplored regions of the world.
A six-month old rhino is cared for at the Moholoholo rehabilitation centre
Presenter Simon Reeve begins the second leg of his journey in the northern part of South Africa, a white stronghold during the apartheid era.
He meets a group of white Afrikaaner farmers who are armed and ready to defend their land in what feels like an increasingly hostile world.
The farmers still own the best land and fear it may one day be taken from them, just like in crisis-ridden Zimbabwe, a short drive to the north.
Thousands of Zimbabweans cross illegally into South Africa every week, fleeing hunger and persecution, and at the border Simon witnesses a dramatic human tragedy as young men struggle through thick rolls of razor wire.
Simon then heads out with the white Afrikaner farmers, who run vigilante patrols rounding up the Zimbabwean refugees. The Boers catch several young Zimbabwean boys and hand them over to the police, who will send them home.
The sun sets in Mozambique's Limpopo National Park
Heading east along Capricorn, there is incredible wildlife in the Kruger National Park, where proposals to cull the booming elephant population are causing huge controversy.
Across the border the beautiful country of Mozambique is still recovering, 15 years after a brutal civil war.
Landmines still litter the country, but an unusual project which uses Giant Gambian Pouched Rats - whose keen sense of smell can detect explosives under the ground - has been employed to clear them quickly.
Much of Mozambique's coast is a tropical paradise, and tourism is a great hope for the economy. But on one island of exclusive 'eco tourist' resorts - where Leonardo di Caprio has holidayed - Simon finds locals living in abject poverty.
Simon flies across the Indian Ocean to Madagascar, the world's fourth largest island.
After the BBC team's baggage fails to arrive Simon heads out to explore the capital, Antananarivo - known by all as Tana - which is a unique blend of African, Indian and French colonial influences.
In the main market Simon's guide encourages him to eat zebu penis soup, an acquired taste, before the bags finally arrive and they fly to the remote south of the island.
Driving across Madagascar, Simon sees one of the poorest but most beautiful countries in the world.
There is a spiny forest, a unique habitat of giant octopus and baobab trees, where Tavy - a form of slash and burn agriculture - has destroyed up to 90% of Madagascar's primary forest. Simon then witnesses men crawling through dangerous underground tunnels in search of sapphires.
His journey ends after he takes a spectacular train journey through the mountainous highlands to the east coast.
Series Producer: Sam Bagnall
Presenter: Simon Reeve
Director: Christopher Martin