As a landscape photographer I'm always looking for unique locations. Living in Arizona, I seek out ghost towns, abandoned mines, and old airfields, military or civilian.
The only drawback is that it originally concentrated on the southwestern United States and California, but the developers are adding new locations every week. Depending on what you are searching for, there are locations in every state and around the world. Searching for "mines" for example has nice coverage in the Midwest and the eastern U.S.
After you enter your search you'll get a Google Map with pins at your selections. You can search for things like churches or mills, or just about any abandoned place. You can also just look at a state and see everything.
Locations are listed in order of distance. When you click on a pin, you'll get a photo of the location, some comments from people who have been there, latitude and longitude, and driving directions.
One mildly disconcerting feature of the app is every so often you'll see a price next to a location. That means someone found a place and you'll have to pay a fee to get the exact location. You can even post your own locations and attach a fee to them. I guess it could be justified by saying the person asking for the fee doesn't want the place over-run with photographers, but frankly these places aren't likely to become photo meccas. You can also post your own locations and attach a price to the specifics. Most of the money will get come back to you, with a small fee going for app upkeep and administration.
People who use Forgotten can create a free account, save favorites, and use the website that has the same information, and it will sync to your favorites.
At any rate, there are plenty of contributed locations that are free, and that's how I've been using the app.
There are a few things that could be better. The app has kind of a rough feel. Maps take 2 fingers to scroll, which is a bit unintuitive, even though the app reminds you to do that.
Some distance calculations were wrong, but on the next use they were correct. You do have to make sure the app is set to use your location.
On iOS when you want directions, the app needs Google Maps. It would be nicer for iOS users if you also had the option to use Apple Maps.
I had a chat with Joe Manier, who created the app. He told me he mostly takes pictures from his drone, and started compiling a list of good locations.
He's had more than 10,000 downloads, and while most of the abandoned locations are in the U.S. there's are now places popping up all over the world.
Forgotten is is a pretty unique app and photographers should find it useful. I found some iOS apps that are similar, including Really Good Photo Spots and Explorest - Photo Locations. Both apps look interesting but require in app purchases to make them fully useable. Neither seem available for Android but there are similar apps for people using that platform.
If part of your passion is finding out of the way lonely, decaying locations for photography Forgotten is worth a serious look.