The 2,000 miles of the U.S.-Mexico border include a variety of extremely different types of terrain. Some of the areas are populous, while others don’t have humans for miles.

And there is some fencing, but hundreds of miles — in part, thanks to that aforementioned terrain — are without any kind of human-constructed obstacles.

But then-candidate Donald Trump’s constant promises of building a wall to prevent undocumented immigrants and terrorists from getting into the U.S. brought the border into clearer view for millions of Americans who’ve never been near it.

The USA Today Network has put together 15 major stories along with an interactive map of the border to explore more about what true wall construction would have to contend with.

To learn more, we spoke with Arizona Republic and azcentral.com reporter Dennis Wagner and Kristen Hare, who covers local news innovation for the Poynter Institute.