The work, "HIM" by Italian artist Maurizio Cattelan, has drawn many visitors since it was installed last month. It is visible only from a distance, and the artist doesn't make explicit what Hitler is praying for, but the broader point, organizers say, is to make people reflect on the nature of evil.
One Jewish advocacy group, the Simon Wiesenthal Center, this week called the statue's placement "a senseless provocation which insults the memory of the Nazis' Jewish victims."
"As far as the Jews were concerned, Hitler's only 'prayer' was that they be wiped off the face of the earth," the group's Israel director, Efraim Zuroff, said in a statement.
However, many others are praising the artwork, saying it has a strong emotional impact. And organizers defend putting it on display in the former ghetto.
Fabio Cavallucci, director of the Centre for Contemporary Art, which oversaw the installation, said, "There is no intention from the side of the artist or the centre to insult Jewish memory."
"It's an artwork that tries to speak about the situation of hidden evil everywhere," he said.
The Warsaw ghetto was an area of the city which the Nazis sealed off after they invaded Poland. They forced Jews to live in cramped, inhuman conditions there as they awaited deportation to death camps. Many died from hunger or disease or were shot by the Germans before they could be transported to the camps.
The Hitler installation is just one object in a retrospective of Cattelan's work titled "Amen," a show that explores life, death, good and evil. The other works are on display at the center itself, which is housed in the Ujazdowski Castle.
The Hitler representation is visible from a hole in a wooden gate across town on Prozna Street. Viewers only see the back of the small figure praying in a courtyard. Because of its small size, it appears to be a harmless schoolboy.
"Every criminal was once a tender, innocent and defenseless child," the center said in a commentary on the work.
Poland's chief rabbi, Michael Schudrich, said he was consulted on the installation's placement ahead of time and did not oppose it because he saw value in the artist's attempt to try to raise moral questions by provoking viewers.
He said he was reassured by curators who told him there was no intention of rehabilitating Hitler but rather of showing that evil can present itself in the guise of a "sweet praying child."