I recently had to create a calendar, to share with a few other people. I didn’t want to give them access to my main Google Calendar, and I wanted it to be visible from a mobile device (iPhones in this particular case, and it just so happened that all involved had an iPhone 5, 5C, or 5S). So I created the calendar in Google, and then tried to view it in the native calendar app on my iPhone, and couldn’t add it to the view on my phone. I even tried deleting and re-adding my Google account, with no success.
After much hair pulling and a fair number of Google searches, I stumbled across this link:
Then all I had to do was select the additional calendar I had just created, and save my changes…
… and then I was able to view my new calendar on my iPhone.