Setting up camp on the first night of the trek across a frozen Lake Baikal. The group of four friends, accompanied by their Russian guide Arkady, pulled their sledges 80 km across the world's deepest lake, taking a break on Olkhon Island. They slept two nights on the ice, in temperatures of -15c. Baikal, the world's largest lake by volume, contains one-fifth of the earth's fresh water and plunges to a depth of 1,637 metres. The lake is frozen from November to April, allowing people to cross by cars and lorries.