Several times, observations and things from the road have generated stories, books, and in one case, a book series. I’m not certain I’ve ever sat down with malice aforethought and said, “I’m going to write a set of novels based on _______.” They just sort of happen, for good and ill. On the gripping hand, more than once I’ve thumped my head gently against a wall when I realized that the written descriptions of a place do not match the reality at all, and I had to gut and re-write large scenes.
A trip through the Czech Republic and Hungary led to the Powers books, although it wasn’t planned that way. It also inspired two of the short stories in Tales from the Uplands. Southern and western Austria also contributed a great number of ideas, some of which stood on their own, some of which shifted around and became bits of other things.
Ground-truthing has been helpful, at least until it requires major re-writes of chunks of books. Topo maps and other things are wonderful tools, as are satellite images, but some details are best seen from on the ground and walked. Walking a place provides a lot better idea of the problems and advantages of similar sites, provided you keep in mind any known changes to the landscape over time. It also gives you scents and sounds that even the best maps and images don’t (yet) provide. The interior of the Rammelsberg Mine is going to appear in an upcoming book. You can’t quite duplicate the scents, sounds, and literal feeling of being inside a medieval mine gallery with photos.
Learning the stories of places tends to kick-start other things. A great deal of Merchant and Magic grew during three weeks in Bruges and northern Germany on and around the North Sea and Baltic. Immersion in the history made what I’d read in books far clearer, and access to the German-language materials helped immensely. Likewise what I learned on this trip, about medieval hazmat and how one hosts the Holy Roman Emperor and his entourage for several weeks, will play into the next Merchant book.
Not everyone has that kind of opportunity. But I think roaming around as much as you can and getting the mental cobwebs cleaned out helps anyone, even if it is going to a dinosaur museum or a state park not far from where you live. The change of scene is what matters. A new-to-me environment is a wonderful thing, most of the time, and it can be within Texas or Oklahoma or New Mexico, not across the Pond. If you can go, go somewhere, anywhere, just a different bit of somewhere.
Cat Rotator's Quarterly 
That always works, and walking the ground DOES give you an appreciation of the reality that you can put into words and give the book(s) more depth.
I’ve walked a couple of battlefields. Lines and arrows on a map are great to show what happened, but aren’t so great at showing why.
Why did Bragg uncharacteristically let his forces off a short leash, and allow them to act with decisive autonomy at Chickamauga?
Because he didn’t have a choice.
He probably didn’t even have a firm idea as to where they were.
And you really need to see the view from Hacksaw Ridge to appreciate what happened there.
Yes. I was perched up at Trifels castle peering out across the Rhine Valley and thinking, “Ye gads, nothing can move without being observed. No wonder they put a castle here.” Another small castle, Werla, controlled access to three rivers. Those rivers led to the mines of the Harz, and to major north-south trade routes from the Baltic to the Med. Once you realize that, “castle in the middle of nowhere” makes a lot more sense.
Their reasons may not make sense to us without seeing the ground and the territory. Maps are not territory.