In the days of the Mayas, cenotes – deep, natural pits on the Yucatan peninsula - provided the only means of obtaining drinking water. But in the mythology of this advanced civilisation, these waterholes and caves were also the entrance to Xibalba – the underworld. All deceased were obliged to pass through Xibalba and wait there until they were called into heaven. It was a place in which one made sacrifices to the gods – objects of daily life, as well as bloody, human sacrifices. To this day, the relics of these acts are still in place preserved underwater for more than a thousand years. The entrance to the underworld begins at a dirty waterhole in the middle of the Mexican jungle overgrown and barely recognisable. But immediately after entry, a hall of breath-taking dimensions and beauty is revealed. As if they were sculptures, stalactites and stalagmites lend the underwater cave an almost sacred ambience. By now, one has succumbed to the fascination emanated by the world’s largest underwater cave system. We accompany four professional research divers to Yucatan – a team of specialists, able to squeeze their bodies through crevices and holes, barely larger than their bodies and who master dives that would push even the most experienced divers to their limits. With them, we penetrate worlds only a few people have ever ventured into. We encounter the remains of human victims, prehistoric fireplaces and primeval animal skeletons and undertake a dive, which takes us from the primeval forest to the open sea. We then enter Xibalba – the place of myths and the dead. In the days of the Mayas - a voyage of no return. Today, this is one of the greatest challenges one can face as a diver – the hidden world of the underwater caves of Yucatan – all filmed in 3D.

Horizon discovers what your cat really gets up to when it leaves the cat flap. In a groundbreaking experiment, 50 cats from a village in Surrey are tagged with GPS collars and their every movement is recorded, day and night, as they hunt in our backyards and patrol the garden fences and hedgerows. Cats are fitted with specially developed cat-cams which reveal their unique view of our world. You may think you understand your pet, but their secret life is more surprising than we thought.

'Flexing' is a dance style forged in far east Brooklyn, at the dead-end of a handful of subway lines. Flex dancers channel the grittiness and crime of East New York into choreographed violence with gun movements, simulated bone-breaking, and the mimicked ripping of hearts from opponent's chests. Through battles dancers gain respect, craft an artistic identity, and sometimes find a sanctuary from the poverty and violence that saturates their neighborhood. No other style of street-dance is this violent, scary, or beautifully theatrical. In this purely do-it-yourself scene, creativity and ambition bring a community together around frequent dance-battle showcases that have begun to attract an international audience and may catapult the best dancers into careers in theater or film. Following a group of dancers for over two years, Flex is Kings explores the hopes and realities of this under-acknowledged and totally unfunded group of urban artists

Once life arrived in the Galapagos, it exploded into unique and spectacular forms. David Attenborough investigates the driving forces behind such evolutionary innovations. We learn that life must be able to adapt quickly in these ever-changing volcanic landscapes. It has resulted in species found nowhere else in the world, such as giant whale sharks and marine iguanas that can spit sea-salt from their noses, dandelion seeds that grow into tree-sized plants and spiders that can blend perfectly into the darkness. Adaptation has been the key to survival in these islands so far, but the story of life in the Galapagos doesn’t end here. The catalyst that triggers these explosions of life remains in place.

No two islands in the Galapagos are the same. The imperceptible drift of a continental plate keeps each island biologically isolated. David Attenborough explores this evolutionary crucible, encountering tortoises that weigh up to half a tonne, finches that use tools and lizards that communicate using press-ups; for Darwin, this was all evidence for his theory of evolution. We see the final footage of the world famous tortoise fondly known as Lonesome George, the last survivor of his species. David Attenborough was the last person to have ever filmed with him. Darwin’s famous visit had a downside – the arrival of man. David investigates the impact we’ve had in these islands, as our influence is a double-edged sword. We’ve disrupted the natural balance but he also believes Darwin would be thrilled with the advances we have made in science. We’re also now uncovering evidence that evolution is more rapid than Darwin could ever have imagined. Whatever wonders the Galapagos Islands hold today, they are only a hint of what awaits them in the future.

Richard Feynman is one of the most iconic, influential and inspiring scientists of the 20th century. He helped design the atomic bomb, solved the mystery of the Challenger Shuttle catastrophe and won a Nobel Prize. 25 years after his death - in his own words and those of his friends and family - this is the story of the most captivating communicator in the history of science.