Open the camera app in your iOS Apple device and scan the QR code below. (Simply position the sqaure code image in the center of your camera and allow it to focus)
A notification saying 'open google.com in Safari' or something to that effect should pop up once the code has been scanned. Tap the notification.
Next it should ask if you want to subscribe to the calendar, tap "Subscribe".
You will now be able to see this calendar in your iOS Calendar app.
Choose which calendar you would like to add in the list above.
Login to your calendar.google.com account.
On the left above 'My calendars' you will see a plus sign to add other calendars, click that.
Select the 'From URL' option.
Copy the URL for your desired calendar as shown above, paste it into the space provided and click 'Add Calendar'.
And thats it, you should now see that calendar on the left under 'Other calendars'.
Start:
End:
Turn on/off the different calendars using the checkboxes below