You can limit the view able area and zoom level of the google map using limit panning settings. Google map plugin provides easiest way to limit panning/dragging so the map stays within certain bounds using limit panning settings.
Step 1 Go to Add or Edit Map and scroll down to ‘Limit Panning Settings’ section.
Step 2 Enable ‘Limit Panning’ tab.
Step 3 Enter latitude and longtitude of south and north west and select any zoom level.
Limit Panning

Step 3At the end, click on the Save Map.

Video Tutorial