A pet owner holds his guinea pig named Riec as Father Francisco bestows a blessing on the pet rodent during a feast day Mass in honor of Saint Anthony, the patron saint of animals, at the Saint Fernando church, in Mexico City, Saturday, January 17, 2015. Many people in Mexico bring their pets to churches to be blessed by the priest on this day. (Photo by Marco Ugarte/AP Photo)

A model poses with a crocodile at Chinchorro Banks, Mexico on June 21, 2018. These crocs had a lot to smile about – sporting huge toothy grins as they posed with stunning models in incredible underwater snaps. The brave models held their breath as they came face to face with the magnificent predators during the daring shoot. Photographer Ken Kiefer took a two hour boat ride to reach the carnivorous crocs at Chinchorro Banks, Mexico, along with his wife and model, Kimber and model, Melodie Trevino. (Photo by Ken Kiefer/Caters News Agency)

Paramedics carry an injured woman out from a subway station after a rush-hour subway train derailment, to be transported by a medical helicopter in Moscow, Russia, on Tuesday, July 15, 2014. A rush-hour subway train derailed in Moscow Tuesday, killing 20 people and injuring at least 150, emergency officials said. Several cars left the track in the tunnel after a power surge triggered an alarm, which caused the train to stop abruptly. (Photo by Ivan Sekretarev/AP Photo)

American artist Robert Wechsler has realized a series of sculptural cubes made from thousands of pennies titled “The Mendicant“. Cubes achieved by notching and joining pennies in perfect orientation to one another. Joined at perpendicular angles, the coins create a lattice structure allowing tunnel like passages of light from certain angles. As one moves around them, the cubes seem to fluctuate from material to ethereal. The number of pennies increases exponentially with the size of the cube. Pictured here are three cubes differentiated with subtitles indicating the exact quantity used.

A competitor reacts ahead of Tough Guy Mudathon event in Perton, Britain, 04 February 2018. The original event which started in 1987 raises money for charity and challenges thousands of international competitors with a cross-country run followed by an assault course consisting of 20 obstacles including water, fire and tunnels. (Photo by Nigel Roddis/EPA/EFE)

A competitor reacts as she takes part in the “Tough Guy” adventure race near Wolverhampton, central England, on January 29, 2017. The Tough Guy event, which is being held for the final time in its 30th year, challenges thousands of competitors to run a gruelling course whilst negotiating over 200 obstacles including: water, fire, and tunnels. (Photo by Oli Scarff/AFP Photo)

A couple hugs while standing near a Christmas tree made out of plastic bins and plastic hampers outside the Museum of History in Monterrey, Mexico, December 4, 2015. The humble Christmas tree has a rich history, from evergreen trees used to symbolise eternal life in Ancient Egypt to tree worship among pagan Europeans. The modern version has its origins in Germany, where the song “O Tannenbaum” is still a festive favourite. Today the traditional tree with lights and decorations appears in cities including Washington, Moscow and Beirut. Alternative constructions range from recycled rubbish in Mexico City to old window frames in Rakvere, Estonia. Whatever the shape or size, the message is the same: Merry Christmas. (Photo by Neil Hall/Reuters)

Beneath the Swedish capital lies an intricate web of underground train lines. More than 90 of the 100 stations in the 110km tunnel system, sometimes referred to as “the world’s longest art gallery”, have been decorated with paintings, installations, mosaics and sculptures by 150 artists since the 1950s. After spending a couple of weeks exploring arctic Norway and Sweden, London-based travel photographer Conor MacNeill headed underground to capture images of the metro stations. Here: A rainbow arcs over a girl on the platform of Stadion station. (Photo by Conor MacNeill/The Observer)