Lake Baikal!The world biggest sweet watered lake. And you can drink from it directly! Really! And it's wonderful blue, and extremly cold in the middle of the summer too (I couldn't swim in it). From Irkutsk you can earch the Olkhon Island, and there is a well-equipped camp, and it's qiuet expensive, but you can use your tent next to the lake. Just take care, not on the sand because there are planty of mosquitoes, only on the rock! And you can hire a bicycle to ride around the island, but you need an empty bottle to fill water. And a hat, the sun is verrry hot.

Really nice place with great views :) People are really friendly, especially if you speak russian and you are not afraid of vodka ;) We have been hosted like members of family. we have been feeded, took for hunting, invited to "Bania" (Sauna) and alloved to use boat, all just for a smile :)
I really recomend place and people

We did a sailing trip on lake Baikal for 2 days. Was super relaxing. Boat with Captain and Guide. Slept somewhere on a beach.  Extremely nice surrounding, water was super flat. Definitely worth while a trip if you want to relax and enjoy. 

Best place ever - ask for an elderly lady that rents out a small house. Basic simple. She also offer russian sauna and wonderful dinner at her place..for a few U$!!! Amazing!