Unless i'm mistaken Denny Mtn is N. of I-90. Definitely some interesting looking albeit very chossy rock there. Pretty easy to approach though.
There does seem to be some stuff on the other side but I haven't tried to get close. If it's the same place i'm thinking of I've stared at it many times and thought it looked interesting.
PP, maybe you could clarify which one you're thinking about? There's tons of old logging roads on the S. side and the PCT and Iron Horse venture through there as well.