I found a ravine with multiple weird things in it.
First of all why is that lava not flowing properly (okay I know this one can be kind of common)
Second of all why are those stone bricks there? I thought it was a stronghold but it wasn't.
Third of all there is a diamond eight vein. I thought those were removed in the Caves & Cliffs update. (I mined the surrounding blocks that way that you can tell that it is a diamond eight vein.)
And last but not least the ruined portal's netherrack and magma blocks replace some of the bedrock making it possible to break through the overworlds bedrock layer. (I took the screenshot from the void that way you could see it replacing the bedrock layer.)

I found this ravine in the seed -861281132 at about -6060 [the y doesn't really matter that much] 8423