'Permanent punishment' Mega-prison at heart of Trump's plan

'Don't stop," said the local in the backseat. "Just slow down and you'll see it."

- Thomas Graham

Soldiers watched the vehicle as it passed the turn-off and the checkpoint. Then a white building flashed through a gap in the trees, a few kilometres from the road.

Without permission from the government, that is as close as anyone can get to the Terrorism Confinement Centre (Cecot), the prison at the core of relations between El Salvador and the US.

President Nayib Bukele bills the prison as the biggest in the Americas, capable of holding 40,000 people, and specifically members of MS-13 and Barrio 18, the two gangs that brutalised Salvadorian society for decades.

It is also where the Trump administration has paid to send 238 Venezuelan migrants, and is a black hole from which no information escapes - except for what the Salvadorian government reveals. The Guardian requested to visit but received no response.

"It's like Guantánamo on steroids," said Juan Pappier, Human Rights Watch's deputy director for the Americas. "These people are outside the US, in a country with no separation of powers. They're in a space essentially ungoverned by law." Three years ago, Bukele declared a state of emergency that has continued ever since, suspending constitutional rights and unleashing the state to take on the gangs, including through mass incarceration without due process.