I'd like to see Lake Baikal. It's an amazing natural wonder. In fact, it is considered the world's fifth ocean.
Lake Baikal World's Deepest Lake
Baikal: The oldest and deepest freshwater lake in the world
Lake Baikal, the worlds oldest and deepest freshwater lake, curves for nearly 400 miles through south-eastern Siberia, north of the Mongolian border.
It lies in a cleft where Asia is literally splitting apart, the beginnings of a future ocean.
More than 5,000 feet deep (1637m) at its most profound, with another four-mile-thick layer of sediment further down, the lakes cold, oxygen-rich waters teem with bizarre life-forms.
One of those is the seals favourite food, the golomyanka, a pink, partly transparent fish which gives birth to live young.
Surrounded by mile-high snowcapped mountains, Lake Baikal still offers vistas of unmatched beauty. The mountains are still a haven for wild animals, and the small villages are still outposts of tranquillity and self-reliance in the remote Siberian taiga, as the forest is called.
http://http://lakebaikal.org
One of the worlds oldest geographical features (formed 25 to 30 million years ago), magnificent Lake Baikal (Озеро Байкал
is the highlight of Eastern Siberia for many. Summer travellers enjoy gob-smacking vistas across waters of the deepest blue to soaring mountain ranges on the opposite shore; rarer winter visitors marvel at its powder-white surface, frozen steel-hard and scored with ice roads. Whether they swim in it, drink its water, skirt its southern tip by train, cycle or dog sled over it in winter or just admire it from 2000km of shoreline, most agree that Siberia doesnt get better than this.
Banana-shaped Baikal is 636km from north to south and up to 1637m deep, making it the worlds deepest lake. In fact its not a lake at all, but the worlds future fifth ocean containing nearly one-fifth of the planets unfrozen fresh water (more than North Americas five Great Lakes combined). Despite some environmental concerns, its pure enough to drink in most places but use common sense. Fed by 300 rivers, its drained by just one, the Angara near Listvyanka.
http://http://www.lonelyplanet.com/russia/siberia/lake-baikal/introduction