There are 6 "a ruined gargoyle" PHs on the walls in that area that can spawn the "an ancient gargoyle". 3 near the square fountain and 3 way high up on the castle walls. There are also 7 "a destroyed gargoyle" PHs in the same area that can spawn "an old gargoyle" (very rare)
Edit: Haven't seen anyone else mention this, but, if you go south out of the city, up the ramp, and then take a right up the stairs you come to a courtyard with a square fountain with a sword in the stone at -8, -220. The building in front of this has 4 "a destroyed gargoyle" PH high up on the roof (no way up there as far as I can tell) that the "an old gargoyle" can also spawn. It popped for me there when helping a guildee get Hunter achievement. So there are really 11 PHs, not 7.
conned even at 55, so lvl is wrong, my group found it right outside the tower with high scale kirn and keeper of tombs. He also droped "a sacred key" which opens all the locked doors (at least the ones i tried to open, i.e. the door in front of high scale kirn, the door to keeper of tombs and the door at the begining of zone accross the large bridge over the massive constructs)
Looted Outcast's Journal Page 35 off this guy a few days ago. I suspect that any of the creatures mentioned in the 'Reactivate the Portals' quest might have a chance to drop the pages.