I don't know how many people have found this, but there's a VERY large explorable area north of of the Temple Corridor in North Ascalon. If you've done the Althea's Ashes quest, the portal is just north of the final temple where the ashes were. The first thing you'll face is hundreds of Hydra. I really mean hundreds. These guys aren't too hard alone, but in groups of 10-15 they can be killer. Bring along fire protection.
After the hydra, there's another huge expance filled with creatures called "abomination"s, also in groups of 10-15. They're weaker than the hydras, but have much more annoying necro-type debuff skills. I have to admit that when I got to that section I had been playing the hydra-infested area for 3 HOURS. It was just me, a friend of mine, and a bunch of henches. Just walking to the area with the abominations from the resurrection point took five minutes, so we eventually decided to give up until we could get a bigger group. The area has a lot of good swag, and probably something cool at the end, but it's VERY long and challenging. I'd love to hear of someone's success in the area.
P.S.: Where can I post suggestions for the Guild Wars developers? I have a couple that I'd really like to write out.

Black Dawn
a.k.a Godfrey Longshanks