Temple of Atal'Hakkar (aka the Sunken Temple) and became flooded with memories of the old days. I've had some good times there, back when the game was fresh and I was a newbie trying to learn more about my class and the world. Back then, the dungeon seemed so foreboding and we didn't think too much of losing countless hours navigating the temple's twisted architecture. Eventually, we grew to hate the place.
First of all, getting to the instance itself was no small task. Surrounding the lake where the temple was, well, sunken, there were elite dragonkin that were a handful for characters of appropriate level for the dungeon. That meant needing to be sneaky (or swift) just getting to the middle of the lake. Once you got inside the temple, you had to deal with mummified trolls, oozes and snakes -- elite as far as I can recall -- just to get to the entrance of the instance! That by itself took a good while. Let's not even talk about getting lost on the way there ... the temple before the instance was a convoluted maze of unnecessary rooms, corridors and levels that was littered with NPCs who didn't drop anything good in particular. Oh, and did I mention that there are a whole bunch of quests that take you all around the world and can only be completed inside the instance? It would've been epic if it wasn't such a pain in the butt.
It was fun for a short while, but I suppose I've grown up enough as a player to recognize that it was simply bad game design. Blizzard has grown up, too, right along with us (or it might be the other way around) and started putting out dungeons that were quick, fun, and significantly less confusing. When Cataclysm finally breaks the World of Warcraft, a lot of things will change and go away. I don't know what Blizzard has in store for the Sunken Temple, but I wouldn't miss it if it finally goes under. There are a lot of things I won't miss, actually, but the Temple of Atal'Hakkar is somewhere near the top of my list. How about you? What won't you miss when Cataclysm changes the face of the game world? What parts of the world wouldn't you mind bidding 'good riddance?'