It pretty much
is a pillbox on tracks.
Try typing 'KV2 Tank' into Google mate, plenty of coverage of service history out there.
By the way, there's something strange about that KV2 picture you posted, it doesn't appear to have the standard hull shape above the tracks, can't recall properly but I have a feeling that it was only a development model that had those curved stowage boxes(?) down the sides... but then 'KV2' doesn't appear to be a genuine Russki name for the thing either...
Cheers,
Adam.