President Donald Trump’s southern border wall project is now considered the most expensive wall of its kind in the world with a price tag of $11 billion, or around $20 million per mile, and counting.

“The cost of almost $20 million per mile cost is four times as much as the most expensive other walls being built.”

The $11 billion price tag was first reported by U.S. Customs and Border Protection last week, the office that is in charge of the wall’s construction. The funds have been used to construct 576 miles of the “border wall system.” But the Trump administration is looking for even more funding.

The Pentagon is looking over a funding request to build an additional 270 miles of wall that the Department of Homeland Security says is needed to block illegal drug smuggling across federal land. There wasn’t a dollar amount attached to the request, according to NPR.

The 2020 spending bill that was passed in December 2019 includes $1.375 billion for border wall construction, but Trump is pushing for more to secure the border. Earlier this month, a federal appeals court overruled a lower court’s order blocking his administration from using $3.6 billion earmarked for military projects.

The Trump administration inherited around 650 miles of border structures from the last two presidents, and if the current administration can complete everything it has set out to do, over three-quarters of the southern border between the U.S. and Mexico will be protected.

Trump’s 2016 campaign for the presidency was marked by calls to “build the wall,” and he looks to be going back to that staple as he campaigns for reelection.

“You’re going to have a wall like no other,” Trump said during a rally in Milwaukee last week. “It’s going to be a powerful, terrific wall. A very big and very powerful border wall is going up at a record speed, and we are fully financed now, isn’t that nice?”

But Trump’s border wall project is proving to be much more costly than projects of a similar ilk in the past. Former President George W. Bush’s 18-foot fence that was installed over a decade ago averaged around $4 million per mile, while Trump’s is five times as expensive at $20 million per mile.

Trump border wall

Part of that is the sheer size of the structure. Trump’s wall is over 30 feet tall in places, and it features an “anti-climbing plate” to detract anyone from trying to scale it.

“The border wall system will include a 150-foot enforcement zone, lighting, cameras, other technology and most importantly an all-weather access road making it easier to respond to (undocumented immigrant) traffic,” Customs and Border Protection spokesman Christian Alvarez told NPR. “So it’s not just going to be the barrier itself.”

Reece Jones, a University of Hawaii geographer, said the U.S.-Mexico border fence is the tallest and most expensive structure of its kind in the world.

“The cost of almost $20 million per mile cost is four times as much as the most expensive other walls being built,” Jones said, who also pointed out that there are over 60 border walls around the world.

Further construction of the wall has hit some roadblocks as the government tries to acquire more private land in South Texas.