I think it was an office building, which would mean that after a certain hour it would indeed be empty - except for reception desk and security, which were both noticeably absent.

And if it's a building that the Hand is using as a gate to their most precious secret, shouldn't there be guards or something?

I completely agree with about the eight episodes thing, by the way. I mean, four main characters with four sets of issues to resolve, and you give them eight episodes for that?