I was doing an initial exploration on a new world and came across a ruined portal structure like none I've seen (or appears in the wiki.) The first point was that it spawned mostly underground in a desert, with just a few blocks above the sand. After some excavation, it became clear this was . . . different. I dug out all the sand, sandstone, and other stone varieties, and only left the obsidian, stone brick (all variants), netherack, magma blocks, iron bars, and gold blocks. This is what I found. It goes down about 15 blocks below the surface, and the loot chest was under some stone brick stairs. Anyone ever seen a structure like this in the overworld before?
I promise, no mods were used in the discovery of this feature. It's a found structure in a solo Bedrock 1.16.200 world. I later found a much smaller one generated inside a hill in a Grasslands biome, with similar extra stone brick variants all around the base. I'm not sure if it's some artifact of the terrain generation when the terrain and the structure overlap like that, or if it's just some ultra-rare variant on the ruined portal.
I agree, that looks like the base model generated for the portal itself. It just looks like the stone brick parts generated multiple times over, layering on top of itself. I did find another buried portal elsewhere in the world, this one in the side of a small hill, and it had similar extra stone brick, but not nearly as much.