I have "seen" it but not as a physical structure.
My understanding it that it occupies a space where four worlds ...or realities/times come together. That is to say they coexist in a kind of aligned space/time.
The image I saw was of a tower consisting of large rings (not a spiral) that while tapering towards the top ...still left a very wide opening or "throat"... the rings had U shapes on them and were slowly rotating counter to each other ...so slow that it was almost imperceivable.
Out of the wide opening in the top came an unusually thick black "smoke" that didn't so much billow out but rather appeared to be pulled into the sky layer above it where it merged with the space outside of this space almost appearing to stretch as it did so.
The whole structure was hollow with perhaps a smaller secondary structure on the inside at the bottom but that would just be a guess.
They were four doorways accessible inside this structure that lead to future and past times... one far and one near.
This structure was built to harness what was already naturally at this site ...and I believe it has been destroyed and rebuilt in different forms throughout time... what I saw was the primal form ...like I said this structure exists simultaneously in some form at 4 different points in time.
I did not seek to see this and knew it as something other then The Tower of Babel only to realize later what it was more commonly known as.