For concentrated mental work, it must be quiet and there must be no visual distractions, especially movement. This means an office with a door I can shut. Cubicles are barely adequate; European-style waist-high cubicles, or "bullpens" are unacceptable. Loud conversations nearby, music, or television, are productivity-killers. I used to be able to listen to music (on headphones) while I worked, but as my appreciation for music has deepened, I now find myself paying attention to the music instead of to what I am supposed to be doing. I have used CDs of nature sounds (rivers and oceans) to mask noise nearby, but this is definitely second-best.
I definitely need natural light and areas of light and shade -- completely uniform illumination is depressing. I also find it helpful to have a window that looks out onto a peaceful scene -- trees or fields. This rests my mind and gives my eyes something to focus on that's more than three feet away.
I strongly dislike all-male environments; they tend to be loud, crude, and competitive rather than supportive. The presence of women encourages better behavior in men.
It's very helpful to have an espresso machine nearby, and a fridge with soft drinks in it!
Deleted - meant to reply to a different column.