If we were to burn NH4Cr2O7 with HgSCN in the Dark Ages in Europe and show it to anyone, it is us who would be burning next on a fiery cross of Inquisition. And it’s no wonder, since this experiment produces a truly marvelous result. At first, as you ignite the mixture of NH4Cr2O7 and HgSCN, all you can see is that it is slowly burning with a reddish flame. After a while, however, a crater is formed in the middle of the burning pile, and then, suddenly, tentacle-like appendages start sprouting from the burning mixture. And you can almost hear the scream of the mad occultist – “Come forth, Kraken! Come forth!” But of course, this is simply a chemical reaction that is called the "Pharoah's Serpent". It was also often sold in firework stores until people realized that it was toxic.

“Echus Chasma is a chasma in the Lunae Planum high plateau north of the Valles Marineris canyon system of Mars. Clay has been found in Echus Chasma that means that water once sat there for a time. Echus Chasma is approximately 100 km long and 10 km wide, with valleys ranging in depth from around 1 km to 4 km”. – Wikipedia

Photo: In this handout image supplied by the European Space Agency (ESA) on July 16, 2008, The Echus Chasma, one of the largest water source regions on Mars, is pictured from ESA's Mars Express. The data was acquired on September 25, 2005. The dark material shows a network of light-coloured, incised valleys that look similar to drainage networks known on Earth. It is still debated whether the valleys originate from precipitation, groundwater springs or liquid or magma flows on the surface. (Photo by ESA via Getty Images)

“The Tibetan Mastiff also known as Do-khyi (variously translated as “home guard”, “door guard”, “dog which may be tied”, “dog which may be kept”), reflects its use as a guardian of herds, flocks, tents, villages, monasteries, and palaces, much as the old English ban-dog (also meaning tied dog) was a dog tied outside the home as a guardian. However, in nomad camps and in villages, the Do-khyi is traditionally allowed to run loose at night and woe be unto the stranger who walks abroad after dark”. – Wikipedia

Photo: A man displays a Tibetan Mastiff he raised during the Tibetan Mastiff exposition on April 7, 2007 in Langfang of Hebei Province, China. (Photo by China Photos/Getty Images)

Takehiko Yagi is a rising star in Japanese photography, and his vibrant pictures of the Hindu spring festival of Holi won the Grand Prize at the fourth annual Nikkei National Geographic Photo Prize. Diving into the Colors of Holi is his first exhibition in the US, on show at Foto Care Gallery in New York until 28 September, 2016. Here: Jaipur, India, 2013, (Photo by Takehiko Yagi/The Guardian)

Built for over a million people, the city of Ordos was designed to be the crowning glory of Inner Mongolia. Doomed to incompletion however, this futuristic metropolis now rises empty out of the deserts of northern China. Only 2% of its buildings were ever filled; the rest has largely been left to decay, abandoned mid-construction, earning Ordos the title of China's Ghost City.

Iguazu Falls are waterfalls of the Iguazu River on the border of the Brazilian state of Paraná and the Argentinian province of Misiones. The falls divide the river into the upper and lower Iguazu. The Iguazu River rises near the city of Curitiba. It flows through Brazil for most of its course. Below its confluence with the San Antonio River, the Iguazu River forms the boundary between Argentina and Brazil.

Festival goers celebrate during the Chupinazo, marking the beginning of the San Fermin festival on July 6, 2011 in Pamplona, Spain. Pamplona's famous Fiesta de San Fermin, which involves the running of the bulls through the historic heart of Pamplona for eight days starting July 7th, was made famous by the 1926 novel of U.S. writer Ernest Hemmingway called “The Sun Also Rises”. (Photo by Denis Doyle/Getty Images)