Ashley Cooper / Glacier at Alkefjellet in northern Svalbard. At the side of the glacier is an unconformity where basalt rock has intruded as a sill between layers of limestone. Svalbard, Norway, July 2013.

Nick Upton / Two Feral pigeons (Columba livia) resting on a window sill, unafraid of a plastic Eagle owl decoy bird scarer, Bath, UK, March.

Nick Upton / Two Feral pigeons (Columba livia) resting on a window sill, unafraid of a plastic Eagle owl decoy bird scarer, Bath, UK, March.

Graham Eaton / Hadrian's Wall between Steel Rigg and Housesteads on The Whin Sill, a layer of hard intrusive, volcanic Dolerite naturally forming high ground, Northumberland, England, UK, March 2017.

Graham Eaton / Hadrian's Wall between Steel Rigg and Housesteads on The Whin Sill, a layer of hard intrusive, volcanic Dolerite naturally forming high ground, Northumberland, England, UK, March 2017.

Graham Eaton / Hadrian's Wall at Sycamore Gap between Steel Rigg and Housesteads on The Whin Sill, a layer of hard intrusive, volcanic Dolerite naturally forming high ground, Northumberland, England, UK, March 2017.

Graham Eaton / Sycamore (Acer pseudoplatanus) in Sycamore Gap, Hadrian's Wall. The wall is constructed on The Whin Sill, a layer of hard intrusive, volcanic Dolerite. Between Steel Rigg and Houseteads, Northumberlan...

Graham Eaton / Elevated view along Hadrian's Wall. The wall is constructed on The Whin Sill, a layer of hard intrusive, volcanic Dolerite. Between Steel Rigg and Houseteads, Northumberland, England, UK, March 2017.

Graham Eaton / High Cup Valley, u-shaped valley with intrusive dolerites of Great Whin Sill exposed on both sides of valley, Appleby in Westmorland, Cumbria, England, March 2017.

Graham Eaton / Jointed intrusive dolerite of Great Whin Sill at High Cup Nick, Appleby in Westmorland, Cumbria, England, UK, March 2017.

Graham Eaton / Jointed intrusive dolerite of Great Whin Sill above u-shaped valley, High Cup Nick, Appleby in Westmorland, Cumbria, England, UK, March 2017.

Graham Eaton / Jointed intrusive dolerite at Great Whin Sill, High Cup Nick, Appleby in Westmorland, Cumbria, England, UK, March 2017.

Graham Eaton / U-shaped valley and jointed dolerite outcrop of the Whin Sill, High Cup, Appleby in Westmorland, Cumbria, England, UK, March 2017.

Graham Eaton / Jointed intrusive dolerite at Great Whin Sill, High Cup Nick, Appleby in Westmorland, Cumbria, England, UK, March 2017.

Graham Eaton / High Cup, u-shaped valley with intrusive dolerites of the Whin Sill exposed at sides, Appleby in Westmorland, Cumbria, March 2017.

Graham Eaton / High Cup, u-shaped valley with intrusive dolerites of the Whin Sill exposed at sides, Appleby in Westmorland, Cumbria, March 2017.

Graham Eaton / The Whin Sill at High Cup with heavily jointed dolerite at top of u-shaped valley, Appleby in Westmorland, Cumbria, England, UK, March 2017.

Graham Eaton / The Whin Sill at High Cup with intrusive volcanic dolerite at top of u-shaped valley, Appleby in Westmorland, Cumbria, England, UK, March 2017.

SCOTLAND: The Big Picture / Pine marten (Martes martes) sitting on windowsill of house, Ardnamurchan, Lochaber, Highland, Scotland, UK, June.

SCOTLAND: The Big Picture / Pine marten (Martes martes) feeding on windowsill of house, Ardnamurchan, Lochaber, Highland, Scotland, UK, June.

Ernie Janes / Potting shed window with flower pots, hand forks, string and trowel on sill.

Ernie Janes / View through potting shed window with hand forks, string and trowel on sill.

Shattil & Rozinski / Two juvenile Great horned owls (Bubo virginianus) perched on a window sill, Denver, Colorado, USA, April.

Floris van Breugel / Sunrise over the impressive Palisades view from Mount Agassiz, John Muir Wilderness, the two most prominent peaks are Mount Sill and North Palisade, below which lies the Palisade Glacier. California,...

Stephen Dalton / Mottled Umber (Erannis defoliaria) on window sill. UK, December.

Stephen Dalton / December Moth (Poecilocampa populi) on window sill. UK, December.

Bryan and Cherry Alexander / Kittiwakes (Rissa tridactyla) nesting on a window sill in the Russian coal mining town of Barentsburg, Spitsbergen, Norway, June 2006.

Oriol Alamany / Domestic cat (Felis catus) sitting on window-sill, next to plants with an American flag, Saint Paul Island, Pribilof Islands, Alaska, USA

Konrad Wothe / Little Owl (Athene noctua) on window sill, Greece

Rick Tomlinson / Monohull "Sill Beurre Le Gall", skippered by French sailor Roland Jourdain during the Europe 1 Star, 2000.^^^ The monohull finished 7th, crossing the Atlantic in 15d 13h 38m.

Rick Tomlinson / Monohull "Sill Beurre Le Gall", skippered by French sailor Roland Jourdain during the Europe 1 Star, 2000. ^^^ The monohull finished 7th, crossing the Atlantic in 15d 13h 38m.

Graham Eaton / Boulders of igneous Dolerite eroded from the Whin Sill exposed in the headland, Cullernose Point, Northumberland, England, UK. December, 2019.

Oriol Alamany / Peregrine falcon (Falco peregrinus) fledgling, perched on skyscraper window ledge at dusk, Torre Realia BCN, Barcelona, Catalonia, Spain. May.

Paul Harcourt Davies / Common toad (Bufo bufo) on a window ledge looking through window at night, Podere Montecucco, Umbria, Italy. September.

Milan Radisics / Red fox (Vulpes vulpes) vixen looking in through window of traditional cottage house, Vertes Mountains, Hungary.

Michael W. Richards / Little owl (Athene noctua) fledgling hopping through broken barn window, lands on window sill outide, before hoping back inside, Somerset, UK, June .

Loic Poidevin / Goat on farmhouse window sill. This goat lives free range on the farm and often climbs into the window for treats. Vendee, France, May

Bruno D'Amicis / Bush hyrax (Heterohyrax brucei) on window ledge of Wonchet Michail Orthodox Church. Near Hamusit, Ethiopia. 2018.

Graham Eaton / Beach with blocks of columnar basalt of the Whin Sill, Dunstanburgh Castle on headland in background. Craster, Northumberland, UK. December 2019.

Graham Eaton / Dunstanburgh Castle on headland of the Whin Sill, eroded dolerite boulders in foreground. Northumberland, England, UK. July 2019.

Graham Eaton / Dunstanburgh Castle on headland of the Whin Sill, eroded dolerite boulders in foreground. Northumberland, England, UK. July 2019.

Robin Chittenden / Peregrine (Falco peregrinus) sitting on windowsill of house, Norwich, England, UK, June.