Structure with it's own portal like the e dragon's spawn?

Hey, so I have a confusing question. I would like to have a structure which can be found in the end, but also has a buildable portal counterpart in the overworld. What I mean is you can create a portal in the overworld that if you go through it takes you to this specific structure in the end. The structure can also be found naturally in the end. I think I can quite easily figure out the natural spawning of the structure in the end but not the portal thing. I'm hoping I can get the portal to be in a different dimension unlike how end gateways work. Kinda like the enderdragon but not in the center of everything.