Catwalks hang over a section of the newly constructed eastern span of the San Francisco-Oakland Bay Bridge during a media tour of the self-anchored suspension span tower on August 29, 2011 in Oakland, California. Contruction crews have erected twelve foot wide catwalks that connect to the San Francisco-Oakland Bay Bridge self-anchored suspension span's tower and crews will begin to lay the nearly one mile of main cable beginning in early 2012. The bridge has been under constrution since 2002 with an estimated price tag of $6.3 billion and will have the world's tallest Self-Anchored Suspension (SAS) tower once completed. (Photo by Justin Sullivan/Getty Images)

People who live in nearby villages make their yearly pilgrimage as they walk up the slopes of the Popocatepetl volcano in Mexico, Wednesday, March 12, 2014. Every year on March 12, residents make their way up the volcano celebrate the day of Don Gregorio Chino Popocatepetl, as the volcano is known to them, with food, music, dance and fireworks. When the sun rises, hundreds of pilgrims head out from the towns of Santiago Xalintzintla, Tlamacas and San Nicolas de Los Ranchos in van and trucks to drive, then walk up the 17,886-foot (5,450-meter) volcano for their daylong celebration. (Photo by Eduardo Verdugo/AP Photo)

Justin Nelzen, in red vest, joins others as they work to rescue up to 70 horses along Cypresswood Drive near Humble along Cypress Creek, Monday, April 18, 2016, in Houston. More than a foot of rain fell Monday in parts of Houston, submerging scores of subdivisions and several major interstate highways, forcing the closure of schools and knocking out power to thousands of residents who were urged to shelter in place. (Photo by Mark Mulligan/Houston Chronicle via AP Photo)

Jacob's Well is a perennial karstic spring in the Texas Hill Country flowing from the bed of Cypress Creek, located northwest of Wimberley, Texas. The twelve foot (four meter) diameter mouth of the spring serves as a popular swimming spot for the local land owners whose properties adjoin Cypress Creek. From the opening in the creek bed, Jacob's Well cave descends vertically for about thirty feet (ten meters), then continues downward at an angle through a series of silted chambers separated by narrow restrictions, finally reaching a depth of one hundred and twenty feet (forty meters). Until the modern era, the Trinity Aquifer-fed natural artesian spring gushed water from the mouth of the cave, with a measured flow in 1924 of one hundred and seventy gallons per second (six hundred and forty liters per second) discharging six feet (two meters) into the air. The spring is the greatest source of water recharging the Edwards Aquifer.

British artist Lucy Sparrow makes her West Coast debut this week with a nearly 2,800-square-foot supermarket in which everything is made completely of the crafting fabric beloved by kindergarten teachers and camp counselors. The installation, which is staged inside the Standard, Downtown L.A. and runs August 1 to 31, is fully shoppable. Here: Lucy Sparrow, 32, adjusts bottles of alcohol on shelves in her art installation supermarket in which everything is made of felt, in Los Angeles, California on July 31, 2018. (Photo by Lucy Nicholson/Reuters)

Fighters from Germany take up position before competing in the Medieval Combat World Championship at Malbork Castle, northern Poland, April 30, 2015. Medieval combat is a full contact sport that revives the foot based tournament fighting of medieval Europe. Countries fight in refereed matches where the objective is to get the opposing team to the floor. There are also duels with polearms, swords and shields where the number of hits landed are scored. The fighters, both male and female, wear heavy armours and weapons, mostly replicas of authentic pieces, and fight following the knights code of conduct. According to organizers, 25 nations from 6 continents are taking part in the Championships, which started on April 30 and will go on until May 3. (Photo by Kacper Pempel/Reuters)

Boys walk home for lunch from school in the village of Kogelo, west of Kenya's capital Nairobi, July 16, 2015. U.S. President Barack Obama visits Kenya and Ethiopia later this month. His ancestral home of Kogelo is home to Sarah Hussein Obama, his step-grandmother. The Kenyan village, burial place of Obama's father, features an open-pit goldmine, a pork butcher's, a school named after their most famous son and outdoor market stalls. Villagers get around by motorbike taxi or on foot while a donkey-cart transports water. Children, some of them named Obama in honour of the President, walk to and from school together. (Photo by Thomas Mukoya/Reuters)

It would seem to be something you'd see only in a cartoon or at a Phish concert, but according to park rangers in New South Wales, Australia, dozens of giant, fluorescent pink slugs have been popping up on a mountaintop there. The eight-inch creatures have been spotted only on Mount Kaputar, a 5,000-foot peak in the Nandewar Range in northern New South Wales. Scientists believe the eye-catching organisms are survivors from an era when Australia was home to rainforests. A series of volcanoes, millions of years of erosion and other geological changes “have carved a dramatic landscape at Mount Kaputar”, the park service wrote on its Facebook page, and unique arid conditions spared the slugs from extinction. (Photo by Michael Murphy/AFP Photo/NSW Environment Office)