Lake Baikal, located in the mountainous Russian region of Siberia, north of the Mongolian border, is the world’s oldest (25 million years) and deepest (1,700 m) freshwater lake. Known as the 'Pearl of Siberia', it holds about 20% of the world's fresh surface water, which is more than all of the North American Great Lakes combined. Home to thousands of plant and animal species, many of which are endemic, it is recognized for its unique biodiversity and is a UNESCO World Heritage Site. The lake's clear waters are surrounded by taiga and steep mountain ranges. The surrounding area, including the Baikal Mountains, offers many recreational activities such as hiking, camping, and winter sports. Olkhon Island, the largest of Baikal's 27 islands, is a popular destination for tourists seeking its natural beauty and shamanistic heritage. The Circum-Baikal Railway running along the coast is a stunning example of engineering from the early 20th century offering breathtaking views of the lake.