Couples take part in a competition during a mass wedding of 64 doctoral student couples at Harbin Institute of Technology, a university in Harbin, Heilongjiang province, China, June 4, 2017. (Photo by Reuters/Stringer)

Convicted murderer Hector Alvarado Mazariegos, right, drops to the ground as he is hit by bullets of a Guatemala firing squad in the public cemetery at Mazatenango, June 28, 1975. His companion, Rocael Ortiz, met the same fate a few seconds later. Both were convicted of murder. (Photo by AP Photo/Anzueto)

A motor taxi driver gets his hands washed at an Ebola screening station on the road between Butembo and Goma on July 16, 2019 in Goma. The first patient to be diagnosed with Ebola in the eastern DR Congo city of Goma has died, the governor of North Kivu province said on July 16, 2019. The case – the first in a major urban hub in the region's nearly year-old epidemic of the disease – has sparked deep concern in neighbouring Rwanda and at the UN. (Photo by John Wessels/AFP Photo)

A boatman rests on his boat in the flooded Ganges river under the Shastri bridge at Daraganj Ghat, in Allahabad, India on August 22, 2019. (Photo by Sanjay Kanojia/AFP Photo)

Students dressed as Hindu Lord Shiva, also known as Nataraja, the Lord of Dancers, during a religious event in Mumbai, India, August 30, 2018. (Photo by Francis Mascarenhas/Reuters)

A woman hangs red chillies to dry outside her house at Khokana village on the outskirts of Kathmandu on August 5, 2020. (Photo by Prakash Mathema/AFP Photo)

Russian policemen detain participants of an unauthorized “Russian March 2020: For freedom and justice! We go out to say that Russian lives matter” organised by Russian nationalists on the National Unity Day in Moscow, Russia, 04 November 2020. Russian nationalists demand freedom for political prisoners in prisons and a fair investigation into the deaths of political prisoners, including representatives of radical movements who were killed during detention or found dead in places of detention. (Photo by Sergei Ilnitsky/EPA/EFE)

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.