'At peace' or 'in peace'?

Hearing her voice puts me at peace.

Hi, Mr. Micawber.

I'd like to understand the reasons somepeople use a certain preposition and others a different one, like in this sentence:

"Let's meet at the office" or "Let's meet in the office"

Which is correct?

And why?

Thanks.

The 2nd person is thinking of the room, the 3-dimensional space, but the 1st person is thinking of the point location (downtown, for instance).

Right. That makes sense. But what about these ones?

1. "Workers shall submitt all requested documentation on time, else then will not be allowed to work IN/ON/AT the Project".

2. "He lives in London, IN/ON/AT Shaftesbury Avenue".

3. "What famous hall is ON/AT the corner of 7th avenue and 55th street in New York City?"



4. "She lives ON