New York: This is the non-specific location of the government residence Jack lives in for a while, as well as the location of many night patrols for G/B. (The night patrol reference is more fully understood once you've read the book)
Las Vegas: This place is visited briefly by G/B and Tori for a reason I won’t mention now.
The Jewel of Africa: This is a future city in Africa based on Abuja, Nigeria. The city of Abuja is sometimes referred to as the Jewel of Africa, but in this story, it is the actual name of the city. The city is the location of the Unit Headquarters.
Adis Abiba & Egypt: Two of the places Mira and G/B visit while in Africa when searching out the Unit and Fred. If these locations were characters they would be mentions, while the others on this list would at least be minors.
Alaska: A cold and mostly remote place making it ideal for hiding the path to the Sacred Place. This place is visited by G/B and he finds that he likes it more than he thought he would.