As much as I love many parts of Midgar, the slums are not included in that love and nor is Shinra Headquarters. Of those two, as dumpy and stinky as the various sector slums are (I do have a place in my heart for sector 7's, I must say), Shinra HQ is far-and-away the place I least want to be at.
Everything about that place turns me off. The people who work there are mostly stuck-up snobs. The upper management treats everyone like they're low-life scum. The layout to the building makes no sense, causing countless new employees to get lost on their first week(s)/month(s) of work.
It just SUCKS! In about every way that a company and a building can suck.