With a lot of people sitting waiting for queues at the moment, I thought it would be fun to compile a thread full of interesting secrets from Vanilla WoW. Feel free to add anything you know!
Outside the Deadmines: The Deadmines dungeon actually sits inside a huge pillar of terrain on a large zone map. A mage could get outside of the actual dungeon by turning around immediately upon zoning in, and casting blink to skip to the other side of the zone portal. There were all sorts of interesting props out there that would end up in later expansions.
Mysterious Dragon: At the very southern tip of Kalimdor, along the coast line beneath Silithus, there is a secret cave. This location is never used for any quest, and there’s no reason to be there at all. Inside the cave is a sleeping dragon that can’t be targeted and has no name.
Mysterious port: If you follow the coast line of the Eastern Kingdoms north from Stormwind, you will eventually come upon a small dock and a shack in the middle of nowhere. There’s no known reason for ever being anywhere near here.
Outside Naxxramas: We won’t be seeing it for quite a while still, but it is possible to get outside of the dungeon map and explore the (very rough) world outside. As well as mixing two different terrain sets jarringly (plaguelands + snow) you can see rough unfinished terrain with prominent hexagonal patterns.
Edge of the world: If you do ever manage to make it to the outer edge of the world map (it’s possible, people have done it) you will be met with a solid line of hexes at the edge of the water, then nothing. As with the edge of all zones, wherever you find one, if you jump into the nothingness your character is suspended in mid air and you will be unable to do anything.