A sick California sea lion with possible domoic acid poisoning is rescued to be evaluated by volunteers from CIMWI (Channel Islands Marine & Wildlife Institute) in Santa Barbara, California, on March 25, 2025. Over a hundred sea lions, dolphins and other marine mammals, including birds, have been sickened by domoic acid poisoning from algal blooms in Southern California since February, US media reported. (Photo by David Swanson/AFP Photo)

Lake Baikal is the world's oldest lake, at 25 million years (possibly older), and deepest, averaging 744.4 metres (2,442 ft).

Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the world, containing roughly 20% of the world's unfrozen surface fresh water.

Competitors in action during a qualifying heat for the 12 hour Lawn Mower Endurance Race on September 24, 2011 in Billingshurst, England. First started in 1973 as a motorsport that would be accessible to as many as possible, there is little commercialism or sponsorship, no cash prizes and no modifying of engines. The trophies are donated from various sources with famous names such as Sir Stirling Moss found engraved on the plaques from previous races. (Photo by Matthew Lloyd/Getty Images)

A woman leaves sauna during the sauna marathon in Otepaa, Estonia on February 2, 2019. Participants have to track down, locate and visit designated saunas in the Otepaa area as fast as possible during the event. The team that completed all of the saunas in the shortest time wins. (Photo by Ints Kalnins/Reuters)

A climate activist wears an oxygen mask to demonstrate the possibility of pumping oxygen from a tree in a bottle in the future, during a protest against the government's deforestation practices of Sri Lanka's main wildlife forests for developments in Colombo, Sri Lanka on March 22, 2021. (Photo by Dinuka Liyanawatte/Reuters)

A villager stretches as the Mayon volcano spews ashes and lava in Legaspi city, Albay province, Philippines, 12 June 2023. The restive Mayon volcano has begun spewing lava and small eruptions, putting the lives of thousands of people at risk from possible violent explosion. (Photo by Francis R. Malasig/EPA/EFE)

“Winter shapes, Moscow river”. Moscow river at this part is never covered by ice. When the temperature is very low it's possible to see a strong fog. Morning light and pipes of the oli factory creates a fantastic landscape. Photo location: Moscow, Russia. (Photo and caption by Sergey Rumyantsev/National Geographic Photo Contest)

A Pelican attempts to take a persons belongings while they are sat in St James' Park, London on Monday, August 11, 2025. Temperatures will soar above 30°C in parts of the UK in the coming days, with another heatwave possible in some areas. (Photo by Yui Mok/PA Images via Getty Images)