After all day, the camera gets to be big and heavy too and a bit hard to disguise....
I use my 24-120mm f/4 AFS VRII frequently. It's a great range and the VR is a significant advantage in a fast moving travel situation. I've recently started using a Black Rapid strap and that's made a huge difference in my ability to carry the load all day. The strap is secure and easy to use, but the carry is exposed. Prior to that I've used a Domke J803 bag that's literally been all over the world with me. I work from the bag and "holster" the camera after each use. It's nice to have both options at your disposal.
Regardless of zoom choice, I also take a fast prime lens to give me the option of "skinnying" down the camera, especially for after dinner walks. The focal length is a matter of choice, but my personal preference is the 35mm f/2 AFD lens. It's a bit dated, but light weight and certainly sharp enough in the center to create good images. It's a standard reportage lens, but now replaced by the 35mm f/1.4 AFS lens which is huge (size and weight). My other choice is a 50mm f/1.4 AFD. These two AFD lenses work well on the D700, are compact and both still adequate in the optics department.
Roger It's still, ISO, aperture and shutter-speed, right?