If you can afford only one stopover on the way, then it should be in Irkutsk. The city is situated on both banks of the Angara River and the biggest attraction is Lake Baikal. It is only 64km away – near enough for a day boat-trip. The old quarter of the city is worth a visit, too.
Lake Baikal, the "Pearl of Siberia", is one of the most beautiful places not only in Russia but on earth. It is the world's deepest lake (1637m) and the water is pure and drinkable. The lake contains one-fifth of the world's fresh water – enough to supply the whole population on earth with drinkable water for 40 years. Baikal is also the world's most ancient lake, with unique flora and fauna: two thirds of the 500 plant and 1200 animal species are found nowhere else, as for example, Baikal's freshwater seal and the omul – the local kind of salmon. In a word, Lake Baikal is the perfect place for a holiday, be it boating, kayak, cycling or hiking in the three nature reserves.