When I double take it usually has to do with attractive men, the fox name Reginald that lives in my neighborhood, or the fact that I'm looking the wrong direction when crossing the street.
Architectural photography is something I usually avoid; it's quite difficult to make noticeably distinct images in the field of architectural photography. What about the building / design strikes you that moves you to take the photograph and possibly waste your time composing, lighting, and getting weird looks from everyone around you?
There's a building on the river that I happened to photograph twice - during the work day and at night. It looks old. A corner building. In the day it was almost ugly: surrounded by scaffolding and noise, refracting light such that its cream color became washed out. That's why it's in black in white.
Night suits it so well, I did a double take.