Lake Baikal is one of those wonders that's hard to believe until it's right in front of you. It is the deepest lake in the world —1.642 metres to the bottom— and the oldest, at around 25 million years; a tectonic rift that is still slowly opening in the heart of Siberia. It holds so much fresh water that if all the rivers on the planet poured into it, it would take almost three hundred days to fill it again, and on its own it contains nearly a fifth of the Earth's liquid fresh water. Russians call it 'the pearl of Siberia' and also, without exaggerating too much, 'the sacred sea'.
Its water is astonishingly clear: on a calm day you can see the bottom tens of metres down. And it is full of life that exists nowhere else: four out of every five species in Baikal are endemic, starting with the nerpa, the world's only freshwater seal, an evolutionary mystery that somehow made its way here. In winter everything changes: the lake freezes into a sheet of ice so pure and blue that you walk over the abyss as if on glass, among trapped methane bubbles and cracks that boom like thunder.
Around Baikal live the Buryat people, of Mongol roots, with their shamanism, their Buddhism and their legends: Olkhon Island, in the middle of the lake, is one of the great sanctuaries of shamanism in Asia. Getting here is a journey in itself —from Irkutsk, on the Trans-Siberian line— and an immersion in the deepest Siberia. It's worth saying without drama: because of the war in Ukraine and the sanctions, travelling to Russia today has its peculiarities (there are no direct flights from the West, foreign cards don't work). This guide is informative and cultural; check the current situation before deciding.
Geologically, Baikal is a unique case: it is neither a glacial lake nor an oxbow lake, but a rift lake, formed around 25 million years ago when the Earth's crust fractured into a tectonic valley that is still widening by about two centimetres a year, which makes it both the oldest and the deepest lake in the world. Its shores have been inhabited since prehistoric times by hunting peoples; around two thousand years ago the ancestors of today's Buryats arrived, with a Mongolic language and culture, and they revered the lake and Olkhon Island as sacred places of shamanism. Russian Cossacks and settlers arrived in the 17th century, founded Irkutsk in 1661 and turned the region into a crossroads of routes to China and a land of exile. In the early 20th century, the epic of the Trans-Siberian Railway faced one of its greatest challenges here: skirting the lakeshore with the spectacular Circum-Baikal branch line. The full story is on our history page.
Read the full history ↓Endless Asian Russia: the border between Europe and Asia in the Urals, the vastness of Siberia and the Trans-Siberian that runs all the way to the Pacific.
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Origins, formation and what the sources say.
Almost every lake in the world is short-lived: it forms from a glacier or a river, fills up with sediment and disappears within a few thousand or tens of thousands of years. Baikal is the great exception. It isn't just any lake but a rift lake: it was born some 25 million years ago, when the Earth's crust in this part of Siberia began to crack and pull apart, opening an extremely deep tectonic valley that gradually filled with water. That rift is still active: Baikal is still widening by about two centimetres a year, like a scar on the planet that never quite closes, and the region is seismically active.
That age and that shape explain its records. At 1,642 metres at its deepest point, it is the deepest lake on Earth; and beneath the water, the floor of the rift is covered by several more kilometres of sediment built up over millions of years. It is also the oldest lake in existence and the largest by volume of fresh water: on its own it holds around a fifth of all the liquid fresh water on the planet, more than North America's five Great Lakes combined. It is about 636 km long and up to 80 km wide, a true crescent of water wedged between mountains.
Its isolation over so many millions of years turned Baikal into a laboratory of evolution. Four out of every five of its more than 3,700 species are endemic: they live nowhere else in the world. The most famous is the nerpa, the planet's only freshwater seal, a mystery to scientists, who suspect its ancestors swam here from the Arctic along some prehistoric river. Also unique are the omul, the fish that feeds the region, and a host of translucent crustaceans and deep-water fish. For all these reasons, UNESCO declared it a World Heritage Site in 1996.
The shores of Baikal have been inhabited since prehistoric times by hunting and fishing peoples, as shown by the rock carvings and archaeological sites along its coasts, some bearing witness to thousands of years of seal hunting. But the culture that has left the deepest mark on the lake is that of the Buryats, a people of Mongolic language and roots who settled in the region some two thousand years ago and who are still the majority on the eastern shore today, in what is now the Republic of Buryatia.
For the Buryats, Baikal is not a lake but a living, sacred being: they reverently call it the 'sacred sea'. Their traditional religion is shamanism, in which spirits dwell in mountains, rivers and rocks, and shamans mediate between the human world and the world of the gods. The heart of this sacred geography is Olkhon Island, in the middle of the lake, home of the spirits who rule the island, and above all Shaman Rock, on Cape Burkhan, a white marble headland with a cave running right through it where, according to tradition, the most powerful of those spirits lives. For centuries it was a taboo place that only initiates could enter.
From the 17th century onwards, many Buryats also adopted Tibetan Buddhism, which arrived from Mongolia, and today shamanism and Lamaism coexist in the region. You can see that blend at the great Ivolginsk Datsan, near Ulan-Ude, the main Buddhist monastery in Russia, with its colourful temples and its monks, a world with a Mongolian and Tibetan feel in the middle of Siberia. The coloured ribbons tied to ritual posts along the shores and on mountain passes are still a reminder that, for the people here, Baikal is a land inhabited by the sacred.
The arrival of the Russians at Baikal was part of the great eastward expansion that, in barely a century, took the tsar's Cossacks and explorers from the Urals to the Pacific. They reached the lake in the mid-17th century, and in 1661 they founded the fort of Irkutsk, on the banks of the Angara River, which would become the region's great city and a crossroads of trade routes to China and Mongolia: the tea arriving from Asia passed through here, and the city filled with prosperous merchants who earned it the nickname 'the Paris of Siberia'.
For centuries Siberia was also the land of exile. The tsarist regime sent prisoners, criminals and political opponents here. Among the most famous exiles were the Decembrists, the noble officers who rose up in St Petersburg in 1825 demanding reforms and a constitution; once defeated, many were sentenced to hard labour and exile in Siberia, and several settled in Irkutsk, where they left a remarkable cultural mark (their houses are museums today) and helped give the city theatres, libraries and an intellectual life that was surprising for such a remote region.
From the 18th century onwards, Baikal also drew naturalists and scientists fascinated by its oddities: the impossible depth, the freshwater seals, the translucent fish. Research stations were founded and the lake became a subject of permanent study. That scientific tradition lives on today at the Baikal Museum in Listvyanka and in the institutes of Irkutsk, which study an ecosystem as ancient as it is fragile.
The event that finally bound Baikal into the life of the country was the building of the Trans-Siberian Railway, the colossal line that from 1891 began laying the tracks that would link Moscow with Vladivostok, more than nine thousand kilometres away. When the works reached Baikal, they ran into one of the biggest challenges of the whole route: the lake's southwestern shore was a wall of cliffs dropping sheer into the water, almost impossible to skirt.
In the early years, while the problem was being solved, whole trains crossed the lake aboard a gigantic icebreaker ferry, the 'Baikal', shipped in pieces from England and assembled on the lakeshore; in the harshest winters, when the ice was too thick even for the icebreaker, tracks were laid directly on the frozen surface to get the carriages across. Finally, between 1902 and 1905, the Circum-Baikal Railway was completed, a feat of engineering that followed the southern shore with 38 tunnels cut into the rock, viaducts, retaining walls and stone bridges, one of the most expensive and difficult stretches of the entire Trans-Siberian.
That railway played a dramatic role shortly afterwards, during the Russo-Japanese War (1904-1905) and, above all, in the civil war that followed the 1917 Revolution: armies, refugees and the legendary Czech Legion all passed along this single line. Decades later, the main line was rebuilt further inland and the old Circum-Baikal section was taken out of service as a trunk route, but it survives today as a spectacular heritage and tourist line, along which a slow train follows the lakeshore through tunnels and past viewpoints.
In the Soviet era, Baikal lived through the clash between its status as a natural treasure and the drive towards industrialisation. The best-known case was the Baikalsk pulp mill, built in the 1960s right on the lakeshore, which for decades discharged waste into its waters and became a symbol of the threat to the ecosystem. Defending Baikal was, in fact, one of the first great environmental causes in the Soviet Union: scientists, writers and ordinary citizens mobilised to protect it, and that pressure eventually paid off. The plant finally closed in the 21st century, and in 1996 the lake was declared a World Heritage Site by UNESCO.
Today Baikal is both a growing tourist destination and an ecosystem that needs looking after. In summer, travellers come to sail, go trekking and explore Olkhon Island; in winter, to walk and skate on the blue ice, an experience that has become famous worldwide. That tourism brings income to a remote region, but also pressures: rubbish, uncontrolled building along the shores, algal blooms and declining species. The authorities regulate access to the national parks along the coast (hence the permits now required to visit Olkhon) and try to balance visitors and conservation.
For the traveller, Baikal remains one of the most extraordinary places on the planet: a freshwater sea in the heart of Siberia, with 25 million years behind it, seals that exist nowhere else, a people who consider it sacred and a winter ice that looks like something from another world. It is worth exploring with respect for its fragility and with awareness of the context: since 2022, the war in Ukraine and international sanctions have shaped travel to Russia. Understanding the geological and human history of this lake (the rift, the Buryats, the exiles, the Trans-Siberian, the fight to protect it) is the best way to look deeply at that horizon of water that Siberians rightly call the sacred sea.
