Full-time feline photographer Andrew Marttila from Washington, D.C., captured blissful expressions of various cats on catnip, which he used to compile a book, “Cats on Catnip”. The photographer dedicated his time to capturing the euphoric expressions of kitties high on catnip – and the results are absolutely hilarious. (Photo by Andrew Marttila/Caters News Agency)

A cenote is a natural phenomenon, a sinkhole in the Earth’s surface. The Yucatan Peninsula in Mexico has an estimated 7,000 cenotes because it is primarily made up of porous limestone. For millions of years, rainfall slowly ate away at the limestone and a huge system of underground caves and caverns was formed. Many filled with water from rain or from the underground water table. When the roof of a water filled cave collapses, a cenote is born. The water found in a cenote may be fresh water, salt water, or both. Structurally it may be completely open, like a lake, almost completely closed with just a small opening at the top, or somewhere in between.

Friends and relatives mourn by the coffin during the wake for Florjohn Cruz, who was killed in a police drugs buy-bust operation, in Manila, Philippines late October 20, 2016. (Photo by Damir Sagolj/Reuters)

Two women cry in grief after armed assailants in a motorcycle shot their loved one in a main thoroughfare on July 23, 2016 in Manila, Philippines. The victim was an alleged drug peddler a claim disputed by his wife and maintained her husband is nothing more than a pedicab driver plying his trade when he was shot in front of her. Philippine President Rodrigo Duterte declared a war on crime and drugs after winning the presidential elections on May 9, 2016. President Duterte has recently been living up to his nickname, “The Punisher”, as Philippine police have been conducting night time drug raids on almost a daily basis. (Photo by Dondi Tawatao/Getty Images)

Since Rodrigo Duterte became president last year, his brutal campaign against drugs has claimed thousands of lives. Human rights groups say he is guilty of crimes against humanity, yet that is scant comfort to those mourning loved ones. Here: Constantino de Juan’s seven children sit on a sofa that still bears the bullet hole from their father’s shooting. Juan was preparing a spaghetti dinner on his daughter’s birthday when he was killed. (Photo by James Whitlow Delano/Funded by the Pulitzer Center on Crisis Reporting/The Guardian)

An activist kicks the shields of the military police officers during a demonstration in the military zone of the 27th infantry battalion in Iguala, Guerrero, January 12, 2015. Activists and relatives of the 43 missing trainee teachers from Ayotzinapa's teacher training college broke into the military zone, located less than a mile from where the students went missing, in an attempt to look for the missing students.The remains of only one of the 43 students has been identified so far. (Photo by Jorge Dan Lopez/Reuters)

A clown plays the violin during the XXI Convention of Clowns, at the Jimenez Rueda Theatre, in Mexico City, Mexico, October 19, 2016. In the wake of the creepy clown sightings in several states of North and South Americas and Europe that caused widespread panic, professional clowns from across Latin America came together at an annual convention in Mexico to give a serious message: “We are clowns, not killers!”. Around 200 clowns took part in the 21st International Clown Convention, dressed in bright coloured clothes and makeup, and chanted the word as they clicked group pictures to counter the “creepy clown” craze. (Photo by Carlos Jasso/Reuters)

s*x workers, wearing decorative skull masks, march through the streets in downtown Mexico City, Friday, October 28, 2016. The women march with candles to an altar dedicated to their departed colleagues, many who died violently at the hands of their customers. This annual procession, tied to the Day of the Dead festivities, has taken place for more than 20 years. (Photo by Eduardo Verdugo/AP Photo)