Jerry Monkman / A man climbs "Top of the Prow" rock on Cathedral Ledge. Echo Lake State Park, White Mountains, in North Conway, New Hampshire, USA. October 2009, Model released

Nick Upton / Alpine / Yellow-billed chough (Pyrrhocorax graculus) flying past waterfall and sheer cliffs of the Cirque de Gavarnie, Haute Pyrenees, France.

Leo & Mandy Dickinson / Great Trango wall in the Karakorum, Pakistan

Troels Jacobsen/Arcticphoto / Dramatic geology with caves sheer mountain peak. Quest Bay, Gough Island, South Atlantic Islands, March 2007.

Troels Jacobsen/Arcticphoto / Dramatic geology with caves sheer mountain peak. Quest Bay, Gough Island, South Atlantic Islands, March 2007.

Nick Upton / Tourists on walkway suspended from sheer cliffs alongside the Radovna river as it flows through karst limestone rocks in Vintgar gorge, near Bled, Slovenia, July 2010.

Mike Potts / Kittiwake (Rissa trydactyla) nesting colony on sheer cliff face, Puffin Island, North Wales, UK, July

Chadden Hunter / Chadden Hunter (scientific consultant), directs the camera into position as the team use a jib arm to swing the HD camera out over a 300 metre sheer drop in the Simien Mountains NP, Ethiopia, to film...

Chadden Hunter / Scientific consultant, Chadden Hunter, directing the camera into position as the team use a jib arm to swing the HD camera out over a 300 metre sheer drop in the Simien Mountains to film the rare Wali...

Chadden Hunter / Wildlife biologist, Dr. Chadden Hunter, standing at the top of a 300 metre sheer drop scouting the cliffs of the Simien Mountains looking for the Walia Ibex mountain goat, for the Mountains episode of...

Chien Lee / View of sheer rock cliff of Mount Roraima, Venezuela

Juan Manuel Borrero / Sheer rock faces in the Cuenca mountains, Spain

Juan Manuel Borrero / Sheer rock faces in Ordesa y Monte Perdido National Park, The Pyrenees, Huesca, Spain

Juergen Freund / Hamersley Gorge - banded iron rock walls in the Pilbara Region, Karijini NP, Western Australia. Sheer walls of rock are layered in colours from red to green and blue to pink depending on the light

Juergen Freund / Hiker in Knox Gorge, Karijini NP, Pilbara, Western Australia. Sheer walls of rock are layered in colours from red to green and blue to pink depending on the changing sunlight

Juergen Freund / Hamersley Gorge - banded iron rock walls in the Pilbara Region, Karijini NP, Western Australia. Sheer walls of rock are layered in colours from red to green and blue to pink depending on the light

Pete Oxford / Kicker Rock / León Dormido said to resemble a sleeping lion. It is an eroded tuff cone whose sheer-sided cliffs are frequented by seabirds eg boobies, frigates and tropic birds.

Pete Oxford / Kicker Rock or Leon Dormido is an eroded tuff cone whose sheer sided cliffs are frequented by Boobies, Frigatebirds and tropic birds, Galapagos Islands, Ecuador

Shattil & Rozinski / Mountain goats {Oreamnos americanus} on sheer cliff face, Mt Evans, Colorado, USA

Angelo Giampiccolo / Stalagmites and stalactites lit in Neptune's Grotto, a deep marine cave in the sheer cliffs at Capo Caccia, Sardinia. ^^^A sightseeing tour to the grotto leaves regularly from the town of Alghero.

Angelo Giampiccolo / Small opening onto the sea from Neptune's Grotto, a deep marine cave in the sheer cliffs at Capo Caccia, Sardinia. ^^^A sightseeing tour to the grotto leaves regularly from the town of Alghero.

Angelo Giampiccolo / The sheer rock can be seen plunging below the clear water on the Italian Mediterranean coast, Marina di Camerota, Campania, Italy.

Eric Baccega / View of Liddon cliffs and Liddon cap, with bird flying along shore, Devon Island, Nunavut, Canada, August 2010

Eric Baccega / View of Liddon cliffs and Liddon cap, Devon Island, Nunavut, Canada, August 2010

Eric Baccega / View of Liddon cliffs and Liddon cap, with bird flying along shore, Devon Island, Nunavut, Canada, August 2010

Eric Baccega / View of Liddon cliffs and Liddon cap, with bird flying low over the water, Devon Island, Nunavut, Canada, August 2010

Eric Baccega / Liddon cliffs and Liddon cap. Devon Island, Nunavut, Canada, August 2010