Rivers descend from their mountain sources to the sea.

From the frozen tundra in the north to the dry forests of the equator, Sir David Attenborough narrates a compelling view of the planet. "Planet Earth" was the first natural history documentary to be filmed in high definition, and now a decade later improved technology has made it possible to capture further details, from elusive animal behaviors to previously inaccessible remote landscapes. In addition to exploring the wilderness, the series examines urban dwellings, focusing on animals that have adapted to city life.

Sir David Attenborough narrates this critically acclaimed series that dives deep into the marine environment of Planet Earth. Although two-thirds of the world's surface is covered with water, scientists know less about the oceans than they do about the surface of the moon. This limited series travels from various coasts to the poles to examine watery denizens ranging from the gigantic blue whale to microscopic coral polyps.

The planet is teeming with myriad life forms, both plant and animal, all interlocked in a struggle for survival. As time goes on, some living things are forced to adapt and change to survive. This series chronicles some of the most unusual, if not downright bizarre, behaviors that living organisms have devised to keep their species alive. The 11-episode series was four years in the making, taking camera crews to every continent and habitat.

David Attenborough journeys across the polar regions of our planet.

The most dramatic wildlife spectacles on the planet.

A follow-up to the 2001 award-winning show "The Blue Planet," this natural history series sees Sir David Attenborough return as narrator and host. A breathtaking exploration of the world's vast oceans, hourlong episodes capture animals and other living organisms in their natural habitat, presenting viewers with a fascinating insight into what life is like underwater. From tropical seas to the harsh conditions of the Arctic, the makers of "Blue Planet II" use modern filming equipment and techniques to shine a light on areas of the planet that humans have never seen before.

Produced by the team that created BBC's "Planet Earth" series, "The Hunt" explores the relationship between predators and their prey. Sir David Attenborough narrates this documentary while the cameras follow the animals in their natural habitats. With a specific focus on strategy, the hunters are examined in detail -- from their use of the environment to their sharp instincts and physical prowess. On the other side of the fence are the hunted, which use their senses and defense tactics to flee when they feel threatened. Each episode centers on a different habitat, and the last one focuses on the state of the planet.

Whenever documentary filmmakers at Discovery Channel and the BBC unite for a project, stellar television seems to follow. "Planet Earth: Africa" stems from this collaboration, as did the breakthrough natural history series "Life" in 2009. David Attenborough narrated that one, and he's back to take viewers on a journey through the vast and diverse continent of Africa. Four years in the making, during which more than 2,000 hours of video were shot, the program consists of six hour-long episodes that feature an array of never-before-filmed species, animal behaviors and previously unknown places. Cameras uncover the extreme dangers of the Kalahari, the dense forests and snow-capped peaks of the Savannah, the dynamic Congo rainforest, the ever-changing climate of the Cape and the massive and parched Sahara.