Step 1: From the main Settings menu, select Privacy
Step 2: Select Location Services
Step 3: Scroll aaaall the way down to the bottom to System Services
Step 4: Scroll about three-quarters of the way down to Frequent Locations. Note: this is where you turn this feature off. Which, just wait for it, you'll definitely want to do.
Clicking through even further, you get a specific location display with dates and approximate timestamps of when you've been there. A co-worker's map of the Thrillist office, above, even shows when he takes his lunch breaks. Uh.
Apple says there's no reason to fear your data being tracked since it's "kept solely on your device and won't be sent to Apple without your consent" and is generally only there to "provide you with personalized services, such as predictive traffic routing."
Sure, OK. But the fact that some simple snooping would reveal to your better half that you definitely weren't "working late" the other night should freak you out just the same.