Wild red-chested cuckoo (Cuculus solitarius) at Kibale Forest National Park, Uganda.

Giles Laurent, CC BY-SA 4.0, via Wikimedia Commons. View source.

Mountaineers descending into Chola Valley, 5,200 metres (17,100 ft) a. s. l., in good weather conditions, with a panoramic view over snow-capped Himalayan peaks to the south of the Great Himalayan Range in Mahalangur Himal, Nepal, Himalayas. Today is International Mountain Day.

Vyacheslav Argenberg, CC BY 4.0, via Wikimedia Commons. View source.

"Unity of humanitarian and technical sciences", Soviet time Bas-relief in Saint Petersburg.

Nikolai Bulykin, Public domain, via Wikimedia Commons. View source.

Val Sinestra. Candlestick fungus (Xylaria hypoxylon) on an erosion field.

Agnes Monkelbaan, CC BY-SA 4.0, via Wikimedia Commons. View source.

Window in the west facade of the Lutheran Fishermen's Church in Born auf dem Darß, Germany.

Radomianin, CC BY-SA 4.0, via Wikimedia Commons. View source.

Salt crystals in the crystallization basin in the museum “Las Salinas del Carmen”, Antigua, Fuerteventura, Spain.

Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons. View source.

St. Nicholas the Wonderworker Church (1766) was relocated from the village of Glotovo, Vologda Oblast to the Museum of Wooden Architecture at the Kremlin in Suzdal, Russia. Today is Saint Nicholas Day in much of Eastern and Western Christianity.

A.Savin, FAL, via Wikimedia Commons. View source.

Milky way seen over the Hochkalter Massif and Lake Hintersee in the German region of Berchtesgadener Land.

Anil Öztas, CC BY 4.0, via Wikimedia Commons. View source.

Self-portrait by Anna Bilińska, 1887.

Anna Bilińska-Bohdanowicz, Public domain, via Wikimedia Commons. View source.

Wild Alpine ibex (Capra ibex) at Creux du Van with the Swiss Alps in the background during sunset.

Giles Laurent, CC BY-SA 4.0, via Wikimedia Commons. View source.

Fortified city of Carcassonne during the blue hour, France. Founded during the Gallo-Roman period, the citadel derives its reputation from its 3 kilometres (1.9 mi) long double surrounding walls interspersed by 52 towers. The medieval citadel, situated on a hill on the right bank of the river Aude, was restored at the end of the 19th century by the theorist and architect Eugène Viollet-le-Duc. In 1997, it was added to the UNESCO list of World Heritage Sites because of its exceptional testimony to the architecture and planning of a medieval fortress town.

Diego Delso, CC BY-SA 4.0, via Wikimedia Commons. View source.

Narrow-banded dartwhite (Catasticta flisa postaurea) on Mimosa pudica, Villa Gerar, Silvania, Cundinamarca, Colombia.

Charles J. Sharp, CC BY-SA 4.0, via Wikimedia Commons. View source.