This might not be that interesting or exciting for some of you, but I’m a true explorer and want to know everything, no matter how small or irrelevant it might be.
Most of you have done Stratholme, maybe several times, maybe now recently with looking for dungeon or back in the days. Then you might have noticed in the end of the instance, outside the Slaughterhouse, there is another exit/entrance with a raid portal. If you’ve seen it you might wonder what it’s for and what’s behind it?
It’s possible to get behind the portal, at least in the uninstanced Stratholme, still it might be different or nothing there at all in the instanced Stratholme.
The portal was originally intended to be the portal to Naxxramas but they changed their mind and the portal never got removed, so it won’t teleport you anywhere. But there is a closed area behind it with an unfinished necropolis floating above and two other unfinished undead scourge buildings.
Syrco Owl 
Very cool! I have heard that was the intended purpose of that portal, but I have never seen the space behind it!
~ Effy
That portal was actually part of the Atiesh chain back on Vanilla. Through that portal is where you would fight Atiesh.
In Stratholme Part Slaughter House is located portal. Ion Hazzikostas revealed that this should be the original entrance to the original Naxxramas, as is the molten core of Blackrock Depths.
Sorry for my bad english, i use Google translater
Just recently ran this and realized they put up a gate. Can no longer go there.
Really? :O I haven’t been there since 2012 when I wrote this post. It’s sad that they close off so many interesting areas even if we’re not meant to go there. It’s fun when there i a way to get there without doing anything illegal.