Welcome to Android Central! Are you asking about a Gallery app, or an actual Gallery directory? The Nexus 5 doesn't have a Gallery app--you need to use the Photos app, which is part of Google+.
Gallery apps in general will show all photos, no matter where they're located in Internal Storage, as long as the directory doesn't have a ".nomedia" file in there as well. So there isn't an actual "Gallery" directory. The Camera app stores photos by default in the /DCIM/Camera directory.