help @ Black Rock Caverns

[jim_bouki]

Hi all, and sorry for my (probably stupid) question...
I recently entered Black Rock Caverns, north-west of Chorrol, finished it off quite quickly (i'm still at a low level), and then checked out the uesp wiki and learned that there's a third level, activated by a hidden lever, somewhere in the caves. Problem is, i can't find that lever and was hoping i could get some help around here, be it directions, description ot the place, screenshot or whatever.
Thanks a lot in advance!