Russians play accordions as they walk near the building of the Federal Security Service (FSB, Soviet KGB successor) in Lubyanskaya Square to mark May Day in Moscow, Russia, Sunday, May 1, 2016. As in Soviet times, about one hundred thousand of cheerful workers paraded across Red Square despite a chilly rain, but instead of red flags with the Communist hammer and sickle, they waved the blue flags of the dominant Kremlin party and the Russian tricolor. (Photo by Alexander Zemlianichenko/AP Photo)

A woman uses a phone to take a “selfie” photo with cat as she stands along the barbed wire fence demarcating the “blue line” – drawn by the United Nations to mark Israel's withdrawal from southern Lebanon in 2000 – while an Israeli Merkava battle tank is deployed nearby, at a position along the border near the village of Kfar Shuba in southern Lebanon on June 11, 2023. (Photo by Mahmoud Zayyat/AFP Photo)

A visitor takes pictures with a smartphone of an artwork entitled “Blue Europe, 2015” by Chinese artist Liu Bolin, on display during the exhibition “Visible Invisible” at the Mudec Museum in Milan on May 14, 2019. Liu Bolin known as “the invisible man” for his photographic self-portraits, focused on a body-painting blending with the surrounding area. (Photo by Miguel Medina/AFP Photo)

A cow carrying a bell and autumn flowers headgear walks by in front of spectators at the traditional cattle show in Schwellbrunn, Switzerland, 26 September 2022. The traditional show in the Appenzell region is held annually in autumn, when local farmers return from the alp with their groomed and cleaned cows to present them on a show ground. “The most beautiful and best performing cows are awarded prizes”, the Appenzellerland tourism office adds on their website. (Photo by Gian Ehrenzeller/EPA/EFE)

“Show us our butts! Mucawana tribe – Angola. In Soba village, the Muhacaona (Mucawana) tribe, perhaps the best place i have visited. They use cow dung and fat to make this so nice haircut, and love the beads. They asked me to make pictures of their backs... and butts to see on the camera screen if everything was perfect!”. (Photo and comments by Eric Lafforgue)

A PSE&G utility worker watches the Navy's Blue Angels and the Air Force's Thunderbirds conduct “a collaborative salute” to honor those battling the COVID-19 pandemic with a flyover of New York and New Jersey, Tuesday, April 28, 2020, in this view from Jersey City, N.J. (Photo by Charles Sykes/Invision/AP Photo)

A student attending a winter military camp reacts during a training session in Ansan, south of Seoul January 3, 2013. Hundreds of students between 11 and 17 years old attend winter boot camp training courses every year. The winter courses range from 4 to 14 days at the Blue Dragon Camp run by retired marines, which also offers summer boot camp for students. (Photo by Kim Hong-Ji/Reuters)

Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)