Lake Baikal by bike
Granted, the area around Lake Baikal might not be among the classical biking tours, but is definitely managable. Riding your bike through the Taiga is by far not as crazy as it might sound at first. Compared to tours in Europe you have to cut back some, though, as no one around here is prepared for bikers. You'll notice this most clearly in Irkutsk and Ulan-Ude, the two large Siberian cities close to both sides of the lake. There is a wide selection of bikes in local stores - mostly high quality products. However, you'll hardly ever see people riding their bikes in daily traffic.
That's the reason why there are no bike lanes on the streets. Bikers are simply not a part of Siberian traffic and car drivers not used to paying attention to them. Glancing over your shoulder when turning right? Never heard of! Therefore, being extremely cautious and stopping frequently to be on the safe side is essential and a lot wiser than pedalling like a madman.
Due to strong air pollution in the cities cycling there is far from enjoyable. Riding outside towns through the gorgeous nature around the lake, though, is marvelous.