The U.S. president’s wall seems like smoke and mirrors, a campaign promise thwarted by the realities on the ground. Barriers already exist on the Mexican border. But they are often overcome.

A “big beautiful” wall. Donald Trump hopes to curtail illegal immigration and deport drug traffickers with slogans and concrete piled up between the United States and Mexico. But his flagship campaign promise is sinking, and it faces some important obstacles.

First, financing. The president estimates the construction cost at $12 billion, the Department of Homeland Security estimates $21 billion. Trump would like to make Mexico pay for it, but Mexico has refused to spend even a peso. Congress has not shown much more enthusiasm.

The Main Cities Are Opposed to the Wall

Next, the reality on the ground. The main border towns are opposed to the wall, conscious that it won’t solve their problems. In addition, there are natural geographic obstacles (rivers, mountains, deserts and canyons) as well as the problem that parts of the border are private property and parts belong to an American Indian tribe. Don’t forget the legal actions brought by environmental associations. Even John Kelly, former Homeland Security secretary and now White House chief of staff, has admitted that such a wall would be difficult to construct. Finally, of the 3,200 kilometers (approximately 1,988 miles) that separate the U.S. from Mexico, almost a third is already “barricaded” with barriers erected by Trump’s predecessors.

To better understand what is happening on the border, Le Temps this week published a series of reports about the wall. We went to meet with the U.S. Border Patrol, to listen to migrants and American Indians and even talked to the nongovernmental organizations that want to identify lifeless bodies found in the Sonoran Desert.

Barack Obama Deported 2.8 Million People

Trump is not alone in deploying an anti-illegal immigrant arsenal. Obama, we tend to forget, deported over 2.8 million people during his term, a record number. But the current president is not only going after perpetrators of rape, trafficking and other serious offenses, as he had announced. Among the 12 million illegal immigrants in the United States, even those who have been present for decades can now be deported for very minor offenses.

Coupled with anti-illegal immigrant raids and measures to limit legal migration, Trump’s wall plan, whether it happens or not, symbolizes an important paradigm shift: It buries the image of the United States as a land of welcome. This isolationist outburst could harm the country’s economy.

Of course, the mere announcement of the plan provoked a decline in attempts to cross the border. But those who are determined to come to the United States will continue to do so, even if it means risking their lives. The wall calculus can be summed up in a few words, as expressed perfectly by Janet Napolitano, Obama’s Homeland Security secretary: “Show me a 50-foot wall, and I’ll show you a 51-foot ladder.”