If you know anything about President Donald Trump’s lofty promises, it’s probably that he wants to build a big, beautiful wall at the US–Mexico border. And on Wednesday, Trump signed an executive order to start turning his vision of a wall into reality.

But just what would a wall look like, and how much land would it have to cover? This video, from Josh Begley at the Intercept, covers the vast distance we’re talking about:

Here's the entire US-Mexico border in 6 minutes. pic.twitter.com/PB7PWl1kYJ — Josh Begley (@joshbegley) October 26, 2016

The video uses 200,000 satellite images to zoom through the US–Mexico border very quickly. It takes almost six minutes to make it through the entire border, stretching the nearly 2,000 miles that separate America from its Southern neighbor — and exposing just what a massive undertaking Trump’s wall would be.

As Kriston Capps wrote for CityLab, the wall would be “the largest infrastructure project since the US highway system.” And it might not be feasible, Capps explained:

Engineers have never shied away from projects that seem impossible, but walling off Mexico is something worse: It’s impractical. Reputational risk, ethical conundrums, and environmental liability each pose significant obstacles to building the project. This wall is a wall unto itself.

There are just so many questions here: Who would actually build the wall, especially with the reputation risks involved? Could the federal government obtain the private property along the border without massive lawsuits? How would the wall deal with rivers, given the environmental and economic concerns involved in blocking off these waterways? Could the wall avoid dividing national parks and endangered species, given that these are supposed to be preserved with as little human interference as possible? And how would the US pay for the wall if Mexico doesn’t, despite Trump’s claims that Mexico will pay?

Trump hasn’t really answered these questions, sticking to his campaign’s theme of giving as few specifics on policy as possible. But these questions are big obstacles, highlighted in the video above by the sheer magnitude of the wall’s scale.

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