Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)

“Diver in Magic Kingdom”. Green Lake (Grüner See) is located Tragöss Austria. In spring snowmelt raises the lake level about 10 meters. This phenomenon, which lasts only a few weeks covering the hiking trails, meadows, trees. The result is magical to watch diving landscapes. Photo location: Grüner See at Tragöss, Austria. (Photo and caption by Marc Henauer/National Geographic Photo Contest)

In this June 29, 2016 file photo, boats docked at Central Marine in Stuart, Fla., are surrounded by blue green algae. The 153-mile-long Indian River Lagoon has been plagued by harmful algae blooms. Water quality testing data analyzed by the AP showed the average phosphorous level – a byproduct of fertilizers and human waste that algae thrive on, rose nearly 75 percent between 2000 and 2016. (Photo by Greg Lovett/The Palm Beach Post via AP Photo)

An array of colours dwarf visitors to the Rainbow Mountains in the Andes Cordillera in Peru in January 2023, which owes its colours to the minerals contained in the soil. The sulfur offers the yellow colour, iron oxide gives the red and copper sulfate is green. In total, it is made up of 14 different minerals. It was probably caused by weather and volcanic activity. (Photo by Guillaume Astruc/Naturagency/Solent News & Photo Agenc)

A common gallinule runs across the water to escape a nearby alligator at Green Cay Nature Center in Boynton Beach, Florida on September 4, 2025. Unlike most waterbirds, gallinules have long toes that allow them to walk on floating vegetation. The species is known for its loud, cackling calls that often echo through wetlands. (Photo by Ronen Tivony/NurPhoto/Rex Features/Shutterstock)

Sisters Martha Syrett, 6, left, and Etta Syrett, 4, right, measure one of Ian Paton's huge pumpkins at Pinetops Nurseries, Lymington, Hants, UK on October 5, 2025. An enormous pumpkin grown by a pair of green-fingered twins has smashed two world records – it is the heaviest and the longest pumpkin on the planet. Ian and Stuart Paton grew the pumpkin which weighed in at 2,819.8 pounds (1,278.8 kg) – the equivalent of about two bulls. (Photo by Ollie Thompson/Solent News & Photo Agency)

Joseph Szabo was a frustrated high-school teacher in need of inspiration – so he started photographing his students, and captured all the angst and excitement of being caught between childhood and adulthood. Here: “Priscilla”, 1969. (Photo by Joseph Szabo/Courtesy of Michael Hoppen Gallery/The Guardian)

This picture taken on May 31, 2018 shows a villager walking between abandoned houses covered with overgrown vegetation in Houtouwan on Shengshan island, China' s eastern Zhejiang province. Houtouwan was a thriving fishing community of sturdy brick homes that climb up the steeply hilled island of Shenghshan, but is now abandoned, with entire houses completely overgrown as if vacuum- sealed in a lush layer of green. (Photo by Johannes Eisele/AFP Photo)