Access to the Hole is obtained in one of two ways:
1 - Bring a rouge with you that can unlock the door.
2 - Buy the key from Rallia Hapera. Of course you have to get the guards to let you in first. Just make sure they like you and ask them for a key to Paineel.

There is a 3rd option, and it still works on Al'Kabore, wiggle through the rocks buy standing and ducking rappidly while pressing forward into the little hole between the rocks.

The Hole is an important zone for a number of reasons, most significant of which are the Epic Quests.