Proloc

This app enables you to make your phone silent on your desired locations and when you have exited those places, your previous ringer mode will automatically be switched back.

You have to specify the boundaries of your location as radius in meters
To mark any place, launch the app, and click on large push pin button which is shown on app launch.

Specify the radius in meters by rotating the knob and hit OK button

If your Gps is turned on, your location would be registered in the app, and your phone would be muted immediately