If you ask Suzy Snyder about one of the most significant artifacts in the United States Holocaust Memorial Museum’s collection, she won’t lead you to a railcar used to deport Jews or into the museum’s heap of shoes taken from Jews before they were murdered in death camps. Instead, she’ll point to an artifact that isn’t even on display in the Washington museum: a sweater.

The sweater is a delicate green, only faded with the passage of time. It was worn by a little girl named Kristine Keren as she cowered in the sewers of Lvov, Poland to avoid being rounded up by Nazis. And for Snyder, a curator at the museum’s National Institute for Holocaust Documentation, it’s a uniquely touching example of the human cost of the Holocaust.

In 1943, Kristine Chiger (she changed her name to Keren after the war) was a seven-year-old living in a ghetto in Lvov, Poland. The green sweater, which her paternal grandmother knit before the German invasion of Poland, was a treasured object. Two years before, Kristine had watched that beloved grandmother being loaded onto a truck and deported, likely to the nearby Belzec death camp. When her grandmother had waved goodbye, a Nazi guard had bashed her head with the butt of a rifle.

Now, Kristine lived a hunted life. During the daytime, her parents worked in a nearby labor camp, and Kristine and her little brother hid in their cramped apartment to avoid being deported. When Nazis conducted random roundups, she’d shove her brother into a suitcase and hide in a corner behind her mother’s bathrobe.

Then, in 1943, life got even worse for Kristine when the Nazis decided to liquidate the ghetto. To avoid being deported to a death camp, Kristine and her family went underground—literally. Her parents bribed a sewer worker to help them and a small group of Jews escape to a small underground tunnel inside the city’s sewer system.

“It was terrible,” she recalled in a 2007 oral history. “It was like going to hell.” She could hear children playing above and cars driving overhead, but couldn’t come up to breathe fresh air or see the daylight.

Inside the claustrophobic tunnel, the family was surrounded by a nearly unbearable stench and the continual sound of water that rose to dangerous heights whenever it rained. Rats ate their food and they struggled with lice, dysentery and measles. Kristine’s father taught her to read and her mother tried to keep up her spirits. The only news of the outside world came from Leopold Socha, the Polish worker who had found them their hiding place. Kristine struggled with depression and watched as other people in hiding lost their grip on reality. Some ran out of the sewer, only to be shot. All in all, the survivors would stay in the sewer for 14 months, only emerging once the Russians liberated Lvov in July 1944.

When Kristine finally climbed out of the sewer, she was malnourished and ill, and her eyes couldn’t seem to adjust to the light. But the eight-year-old still had her sweater—and as she recovered and grew, it became a prized possession. “The sweater was saved, together with me,” she recalled. “I cherish this sweater.”

After the war, Kristine moved to Israel, married, became a dentist and emigrated to the United States, where she changed her last name to Keren. She kept her sweater and looked at it daily.

Then, in 2004, she donated the sweater to the museum. It toured the country before finding its way into the museum’s permanent collection. Today, the fragile garment is not on display in the museum itself. Still, it’s a popular object and can be viewed by request.

“It’s the thing that links [Kristine Keren] to her grandmother who did not survive,” says Snyder, who helps collect and care for millions of objects that show the prewar, wartime, and immediate postwar experiences of victims of Nazi persecution. “I think it was very hard for her to make the decision, but it has generated quite a lot of discussion.”

The touching piece is one of Snyder’s favorite objects in the museum’s collection, in part because it resonates with so many visitors, all of whom have a favorite piece of clothing and many of whom associate clothing with loved ones. “It’s personal,” she says.

Snyder and her team travel all over the country acquiring objects; others come their way via people with no personal connection to the Holocaust who spot them on eBay or at estate sales. Surprisingly, she says, even more artifacts have been donated in recent years. And since the collection is completely open-access, any visitor can easily request and access its millions of objects.

One such visit resulted in a unique tribute to Kristine Keren and her sweater. In 2014, a knitter named Lea Stern visited the museum to study the sweater. She then created a replica pattern that she sells on Ravelry, a social media site for people who knit and crochet. All proceeds benefit the museum. (Stern also gave Keren a newly knit replica sweater.)

Kristine Keren’s sweater may have come full circle, but the work of Snyder and other curators at the National Institute for Holocaust Documentation continues. Right now, Snyder is particularly interested in artifacts that document the times before and after the war—symbols of the rich lives Jews lived in prewar Europe and in displaced camps, Israel and elsewhere after their lives were torn apart.

“The more we can document what prewar life was like, the more we can get rid of this idea that Jews were not people,” she says. “They were businessmen and lawyers and doctors and farmers. They had communities that were discarded.”