Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

Yakutsk, with a population of around 270,000, holds its own title: that of the coldest city on Earth. Here: Frost-encrusted house in the city centre. (Photo by Amos Chapple/Courtesy Images/RFE/RL)

Beautiful red sunset sky over Edinburgh, Scotland. Edinburgh is the capital city of Scotland and a popular tourist destination. It is also a major European financial (fund management) centre. Prominent buildings from left to right are: Edinburgh Castle, The Balmoral Hotel Clock Tower and The Scott Monument. (Photo by John Lawson/Getty Images)

A cyclist rides in al-Qudra desert in the Gulf emirate of Dubai, on June 8, 2020. (Photo by Giuseppe Cacace/AFP Photo)

A woman looks at the honour guard soldiers marching at the Tomb of the Unknown Soldier by the Kremlin wall, in downtown Moscow, on June 28, 2021. (Photo by Alexander Nemenov/AFP Photo)

Britain's Catherine, Duchess of Cambridge, shelters from the rain under an umbrella as she arrives at the London School of Economics to mark the launch of The Royal Foundation Centre for Early Childhood, where she took part in a roundtable discussion on the Centre's inaugural report, “Big Change Starts Small” which was released today, in London on June 18, 2021. (Photo by Richard Pohle/Pool via AFP Photo)

Storks casts shadows as they search for food on the dried-up Lake May in southwest Turkey on October 30, 2021. (Photo by Seyit Konyal/Solent News)

Castle rising in the mist on April 14, 2022. Castle Rising is a ruined medieval fortification in the village of Castle Rising, Norfolk, England. It was built soon after 1138 by William d'Aubigny II, who had risen through the ranks of the Anglo-Norman nobility to become the Earl of Arundel. (Photo by Terry Harris/The Times)