How do I take a 3D Flyover tour in Maps in iOS 8?

The Maps app in iOS 8 has a cool new feature - 3D Flyover tours of select cities, national parks and monuments. So far, Apple lists a little over 90 available tours, but not all of them are actually ready. There are cities you'd expect, like New York, Paris and London, and there are some you wouldn't, like Tulsa and Perugia, Italy. There are also some national parks like Yosemite, and monuments like Stonehenge. The tours also provide labels for points of interest. To view a 3D Flyover on your iPhone or iPad, search for your target location; if one is available it will pop up. Tap start and away you go.