To access one of Google Maps' best hidden features, you have to know the magic word. Well, it's a phrase, really, and that phrase is: "OK Maps." Enter this phrase into the Google Maps app and the portion of the map that's currently visible on your screen will be saved directly to your device. Once saved, you can access that map even without a data connection.

It's way better than just taking a screenshot, because your saved map lets you zoom in for greater detail. Also, it works on both iOS and Android devices.*

Here's how to do it. Zoom in on a part of a map that you want to save for offline browsing. Then, tap the search bar and type "OK Maps" (minus the quotes) and hit the Search button. You can also speak this into the phone – just speak "O" and "K" with a slight pause between them, otherwise your phone may spell it as "Okay" and this trick won't work.

If all goes well, you should see a prompt indicating that the map is downloading. It will take about 10 seconds, depending on the size of the map you've selected and the speed of your internet connection. Wait for the message that says "The on-screen map area has been cached," and you're good to go.

The next time you open Google Maps and there's no signal available, you'll be able to view and browse your saved map. It's especially helpful on Wi-Fi-only iPads or Android tablets, and for when your device is in airplane mode. For example, you can virtually explore the area around your hotel while you're flying to the city you'll be visiting. And speaking of foreign travel, this is also very helpful for exploring cities where data roaming is excessively expensive and public Wi-Fi spots are rare.

You'll still need some kind of data signal to get directions, and for real-time navigation. You will also need GPS access in order to pinpoint your exact location on your saved map. But your phone's compass works all the time, so even if GPS isn't available, you can still get your direction sorted.

When I first tried this, I got overexcited and tried to download the entire state of California, which resulted in a most un-Google-like grammatically confusing error message: "The on-screen map are too large, zoom in first." Turns out, it will only cache street data up to about 10 miles away. Large enough for most cities, but not for a whole county. I was, however, able to save a large swath of San Francisco, as well as the entire South Bay region. Not too shabby.

*Yes, Nokia's Here Maps and the iPhone-native Apple Maps also offer this, but the "OK Maps" trick in Google is cool, and largely unknown, and we wanted to tell you about it.