Visitors watch ice-cold artworks, depicting Marilyn Monroe, at an ice and snow sculpture exhibition made by 35 international artists, who worked 4 months at minus eight degrees Celsius in Oberhausen, Germany, on the 1st of Advent, Sunday, December 1, 2024. (Photo by Martin Meissner/AP Photo)

In this photo taken with a long exposure, a person walks a dog past Christmas lights in a park, Sunday, December 15, 2024, in Lenexa, Kan. (Photo by USA Today)

The aerial photo taken on November 20, 2024 shows a general view of buildings during a foggy day in Yinchuan, in northern China's Ningxia region. (Photo by AFP Photo/China Stringer Network)

Aoife Brack (Gorey, Wexford) with Sean Brack on her shoulders having great fun with the Bubble performers at the Kaleidoscope festival in Russborough House, Co. Wicklow, Ireland on July 2, 2023. (Photo by Nick Bradshaw for The Irish Times)

Two young women jump into a pool on the beach on June 20, 2025 in Margate, United Kingdom. Yellow heat health alerts have been issued by the Met Office with temperatures set to climb as high as 33°C by the weekend. (Photo by Leon Neal/Getty Images)

A servicewoman of the 65th Separate Mechanized Brigade of the Ukrainian Armed Forces attends a military drill near a frontline in Zaporizhzhia region, Ukraine on August 11, 2025. (Photo by Ukrainian Armed Forces via Reuters)

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.