Pakistani truck drivers from different cities sit on the roof top of the buildings at Truck station offering Dua before breaking the fast during Holy month of Ramadan in Lahore on April 15, 2021. Ramadan is marked by daily fasting from dawn to sunset Islami's holy month of Ramadan-ul-Mubarak is celebrated by Muslims worldwide marked by fasting, abstaining from foods, sеx and smoking from dawn to dusk for soul cleansing and strengthening the spiritual bond between them and the Almighty. (Photo by Rana Sajid Hussain/Pacific Press/Rex Features/Shutterstock)

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.

To an outsider, their passion is at times illegal and often on the verge of life and death. But climbing rooftops of high-rise buildings and exploring abandoned facilities is in the blood of these young Muscovites. The small group calls itself “Rudex”, which stands for “roof and decay exploration”, and is akin a Western youth craze known as urbex or “urban exploration” of man-made structures. Here: Urban explorer Vad Him of Rudex team jumps whilst on a rooftop in Moscow, Russia, August 14, 2017. (Photo by Maxim Shemetov/Reuters)

A guest poses for photographs at the infinity pool of the newly-inaugurated Dolce Hanoi Golden Lake hotel, the world's first gold-plated hotel, in Hanoi on July 2, 2020. It even has a gold-plated infinity pool on the roof. The 400-room, 25-storey property will operate under the American Wyndham Hotels brand. Prices start at $300 a night for rooms, or there are apartments to rent costing from $6400 per square metre. (Photo by Manan Vatsyayana/AFP Photo)

Cooperation is key to success. This motto was used by the Government of Denmark when they decided to create a project that bore the name of UN City. This compound was designed to house all nine Copenhagen based UN agencies under a single roof. This embodies the core idea of the United Nations, since this project allows for better efficiency and practicality thanks to joint effort. The first plans for the UN City were hatched in 2002. After 11 years, in 2013 the first stage of the project was finally finished. Presently, Campus 1 of UN City accommodates 1,300 staff member, while Campus 2 is going to become the largest humanitarian warehouse in the whole world.

Young Buddhist novice monks play at a Tibetan nomadic summer grazing area on July 24, 2015 on the Tibetan Plateau in Yushu County, Qinghai, China. Tibetan nomads face many challenges to their traditional way of life including political pressures, forced resettlement by China's government, climate change and rapid modernization. The Tibetan Plateau, often called “The Roof of the World”, is the world's highest and largest plateau. (Photo by Kevin Frayer/Getty Images)

Dajana Djuric, 25, who has worked as a chimney sweep since the age of six, cleans a chimney in Brcko, Bosnia and Herzegovina. Dajana Djuric, believed to be the only female chimney sweep in Bosnia and Herzegovina, has to contend with perilous roofs in the depth of winter. (Photo by Dado Ruvic/Reuters)

World Champion Trials bike rider Jack Field of Australia poses after performing the highest backflip on a motorcycle ever recorded as he flips his motorbike upside down on the roof of Melbourne's Eureka Tower (297.3 metres) during a AUS-X Open media opportunity at Eureka Tower on May 22, 2019 in Melbourne, Australia. The largest international Supercross and action sports event in the world outside of the USA, the AUS-X Open will be held at Melbourne's Marvel Stadium on November 30 2019. (Photo by Scott Barbour/Getty Images)