edit:
1. go out on the platform like on the screenshot: svetlojarsk_rockaccess.jpg
2. jump down of the lower plateau
3. go left, untill you see the crack or hole: svetlojarsk_rock02.jpg (maybe it's a little bit lower, i don't dare to go farther)
4. if you go in the crack, you can't climb up again. move a little bit, and you fall in the "cave".
5. now you can't leave the cave