Lake Baikal is like a little reverse-Madagascar.
It’s tucked away in Siberia and, in fact, very little was known about it until it got in the way of the Trans-Siberian Highway, which presumably makes the Trans-Taiga in Quebec look like a bike trail. As Baikal is rather big – it allegedly contains as much water as all the Great Lakes combined – building around it took quite some time.
Two-thirds of the region’s fauna are found nowhere else in the world. This is what brings Madagascar to mind – Madagascar’s unique ecosystem is of land isolated by water; Baikal’s is of water isolated by a zillion miles of land.
The picture there is Olkhon Island, the second-largest lake-bound island in the world.
All in all, one of the most interesting articles I’ve found on Wikipedia.