A sculpture garden in the English countryside seems an unlikely place to explore the shadowy history of the CIA. But Alfredo Jaar’s new work, The Garden of Good and Evil (2017), has quickly become a popular destination at the Yorkshire Sculpture Park in the north of England. Nearly 5,000 visitors experienced the installation during its opening week, a spokeswoman tells artnet News. Unveiled on October 14, the work is a series of prison cells surrounded by a “forest” of 101 trees.

The piece refers to the CIA’s “black sites”: secret prisons created by the US intelligence service around the world after September 11, 2001. Jaar spent years researching the unacknowledged prisons, which are believed to operate in Thailand, Romania, Afghanistan, and other countries.

“It is like a fairy tale—you walk through the forest and then there is the terror inside,” notes Clare Lilley, the director of programming at the sculpture park. She has organized the commission and accompanying solo show, the New York-based, Chilean-born artist’s first major institutional exhibition in the UK.

Lilley is determined to find the powerful work a permanent place in the park’s rolling hills. But the process is more complicated than it sounds. Planting the work’s fir trees—which are currently installed in wooden containers—is not straightforward in the historic countryside; the Yorkshire valley is a protected landscape. “We have a pretty good idea of where we want it to go but we have to go through planning,” she says.

So until April 8, the trees will remain in their planters. But they still manage to create an ominous feel. A group of them is placed right up against the glazed walls of the sculpture park’s Underground Gallery. “The darkness they create inside the gallery and the shadows are really interesting,” Lilley says.

The cells—some cages, some windowless structures—are hidden within the grid of trees. The roofless cages frame the sky—but not in a Turrellesque way. You cannot lie down inside and look up, as they are only one square meter wide. Meanwhile, other cells are barely tall enough to crouch inside.

Lilley was concerned that people would not like the work. But in fact, “the reaction from the public has been incredible,” she says. “People are saying this issue needs to be discussed. Alfredo is dealing with such difficult things we don’t know how to confront.”

The issues raised include the UK government. “We are complicit,” Lilley notes, referring the island of Diego Garcia, a British territory in the Indian Ocean that is allegedly home to a black site. The UK government forcibly removed the island’s inhabitants during the Cold War so that the US could create a military base there. After September 11, the island has reportedly been used as a stop-off for so-called rendition flights of prisoners to other black sites.

Alfredo Jaar: The Garden of Good and Evil, Yorkshire Sculpture Park, October 14–April 8.