I don't know what "Iron Mountain" was, but it isn't currently there because all of this is part of a construction site. The road running along the south side of Smithfields market is completely closed off as part of the construction site https://www.instagram.com/p/DY7nUmwtqLs/, likewise the little road to the east of this block: https://www.instagram.com/p/DY7naxPtOUC/  I think this block itself is also being refurbished if not demolished.

I've updated the construction area to more clearly show that this road is part of it (completely blocked off) : https://www.openstreetmap.org/changeset/183368163  (also merging an unnecessary multipolygon into one construction area)

Maybe some shops/bars/POIs will re-appear here after all the work, maybe even with their original names, but... for the moment "Iron Mountain" means nothing.