Kirkendall-Spring / Doorway of the poet Dilgo Khyentse Rinpoche's house, near Paro, Bhutan, October 2014.

TJ Rich / Young springer spaniel sitting on doorstep. Wiltshire, England, UK.

Ashley Cooper / House surrounded by flood waters by the banks of the River Rothay in Ambleside, in the Lake District on Saturday 5th December 2015, during torrential rain from storm Desmond. England, UK, December 201...

Ashley Cooper / Polar bear (Ursus maritimus) skin killed by an inuit hunter in Ilulissat, Greenland, July 2008.

Franco Banfi / Local woman sitting in front of her house, Camaguey, Cuba, Caribbean Sea, Atlantic Ocean. November 2007.

Aflo / Black cat sitting in front of blue door.

Iris Thorsteinsdottir / Siberian forest cat (Felis catus) grey, ginger and white female kitten age 7 Months sitting by door. Clifton, Bristol, UK.

David Noton / Blue doorway with Grape vines (Vitis) Puyloubier, Var, Provence, France, October 2012.

Ross Hoddinott / Long exposure waves on beach in front of Durdle Door in late evening light, Dorset, UK, April 2013.

David Woodfall / Flooding outside house with debris in front of door during February 2014 floods, Upton upon Severn, Worcestershire, England, UK, 9th February 2014.

Pat Tuson / Old door in front of skip offered for recycling with a note saying Please Help Yourself, Highbury, London Borough of Islington, UK

Pat Tuson / Old door in front of skip offered for recycling with a note saying Please Help Yourself, Highbury, London Borough of Islington, UK

Charlie Summers / Red-billed hornbill (Tockus erythrorhynchus) feeding its mate who is sealed in its nest in the tree. This nest had a front door and a back door, one door is where the male is feeding the female and an...

Eric Baccega / Traditional front door on Ouessant Island, Ile bretonne, Bretagne, France, June 2005

Stephen Dalton / Front door, entrance to house, with standard flowering tree in pot, England, UK

Mark Moffett / Door-maker Ant (Stenamma alas) using mud ball to close entrance to nest, Rio Toachi, Ecuador. Sequence 3 of 3

Mark Moffett / Door-maker Ant (Stenamma alas) closing nest entrance with mud ball used as a door nearby, Rio Toachi, Ecuador. Sequence 2 of 3

Mark Moffett / Door-maker Ant (Stenamma alas) at nest entrance with mud ball used as a door nearby, Rio Toachi, Ecuador

Mark Raycroft / Bernese Mountain Dog (Canis familiaris) sitting at front door

Mark Raycroft / Great Dane (Canis familiaris) with mantle coloration sitting by front door

Mark Raycroft / Golden Retriever (Canis familiaris) puppy laying in front of barn door

Mark Raycroft / English Bulldog (Canis familiaris) three adults looking out of screen door

Mark Raycroft / English Bulldog (Canis familiaris) three adults looking out of screen door

Mark Raycroft / English Bulldog (Canis familiaris) adult portrait inside barn door

Mark Raycroft / Border Collie (Canis familiaris) sitting at front door of house

Mark Raycroft / Weimaraner (Canis familiaris) pair sitting on either side of door, mimicking statues

Mark Raycroft / Boxer (Canis familiaris) standing at door waiting to get out of snow

Kim Taylor / Blue tits (Parus caeruleus) competing for cream at the top of a milk bottle. Surrey, England, UK, August. Digital composite

Kim Taylor / Blue tit (Parus caeruleus) drinking cream from milk bottle. Surrey, England, UK, August. Digital composite

Duncan Usher / Red Fox (Vulpes vulpes) in front of house door at night, Europe

Mark Raycroft / Shetland Sheepdog (Canis familiaris) pair at door

Mark Raycroft / Standard Wire Haired Dachshund (Canis familiaris) trio

Yashpal Rathore / Tiger (Panthera tigris) female, walking through carved door entrance gate of ruins of Bandhavgarh Fort at night, Bandhavgarh Tiger Reserve, Madhya Pradesh, India. Endangered. Camera trap.

Milan Radisics / Female Red fox (Vulpes vulpes) leaving backyard through a traditional wooden door at night, Hungary. January.

David Tipling / Three Barn swallow (Hirundo rustica) fledglings perched on a barn door begging for food, Briston, North Norfolk, UK. September.

Eric Baccega / Kayan Lahwi woman with brass neck coils and traditional clothing sitting next to the front door of her home. In the background stands a buddhist altar. The Long Neck Kayan (also called Padaung in Burm...