Camera
The camera icon allows you to enter photo mode. This mode is just that. A way to take a photo of your City without the Interface and also, at an angle. However, be careful when pressing this button / entering this mode. As it seems to take a rather heavy toll on the performance. Some weaker phones may need to exit and restart the app to make the game run smoothly.
Also, if your device can handle it, going into camera mode is a good way to easily harvest vehicle bonuses as it allows you to still tap on the rewards but not on any Building.