I'm not much of an explorer and while this isn't impressive compared to some other places people go, someone might find this interesting.
To get into Highmaul you can be any class, but need a Day of the Dead Costume such as "Night Demon" Contender's Costume - Item - World of Warcraft
Start by going towards where the raid enterance is:
Then take a left and go along the grass
Until you reach:
Position yourself about here and use your costume:
Then use the leap to get on top of the rock to the right:
Then jump left:
And jump and tap forward to climb the crack:
Once you reach the top just jump onto the hill
You won't slide offf
You can run around most of lower highmaul and there are a few unattackable mobs there:
Interestingly enough, if you get within aggro range you get ported out.