14 floors underground? Seriously? I'm majorly impressed. I had no idea such things existed outside of science fiction. That's a pretty long way down to dig, first of all, and to then create such an expanse at that -- and not just a solitary skyscraper's limited square footage per floor -- is unbelievable. Theoretically, if one-third of Tokyo had that sort of subterranean infrastructure, the entire city -- all xx million of them -- could go underground to shelter a tsunami, an airstrike bombing, etc. That's just nuts. In a very cool way.
And what brought you there, anyway? Don't tell me the main subway system is that deep! (I'd have thought four to five stories tops.) From the photos you took, it looks sort of like 50% shopping mall merged with 50% basement of an office building. The people mostly looked like blue collar workers (in at least one of the photos). Is it a popular shopping district? or is it a place few people commonly frequent?