Caves on the lake
A rather unknown but waste field that hasn't been discovered by foreigners so far are the underground treasuries of the region. There are some dozens (or even hundreds?) of caves, which are partly inaccessible or only reachable with great logistic effort. Other ones can easily be discovered and visited by "normal" wanderers.
Next to difficult (but interesting) systems like the polytechnic cave at Pribaikalsk national park or Ikoninskaja at Kitoj there are several easily accessable and smaller caves. At the west shore of the lake Baikal in the area of Bolschoi Kodilnij there are caves and grottos that are reachable within two days of walking at the most, e. g. Tschasovnja (the Chapel) and Mochovaja (the Mossy) - just to mention two. A bit harder to reach are the caves at Buchta Aja, which are beautiful and partly decorated with icicles. Both regions are also worth a visit for the charming scenery.
If you want to hike the gorgeous Kitoj you will find a huge collapsed doline (Kosi Dvor; doline = a sinkhole caused by collapsed ground formation) about 70 km from Angarsk at the north shore. It opens up to the valley and presents awesome ice stalagmites until late summer months.
There are more cave systems at the east side of the Sajan Mountains. Be aware that there is more effort needed to visit these ones. For beginners caving is only recommended in professional company! These systems are often far away from civilisation or they can only be explored by speleological technics and might not be mapped.
If you are interested in larger undertakings (mapping or photography expeditions, cavings, etc.) you should adress Baikalplan e.V. in Dresden. They can arrange contacts to speleologists in Irktusk. This is advisable in any case since both the finding and the visit itself should always be done in company with experienced speleologists!
Motto: Do not take, leave or destroy anything and do not kill anything!
An important point in this context is the protection of caves. That stalagmites and other sinters should not be removed or destroyed should be a matter of course. This applies also to writings on walls like "I was here 1923".