Two-year-old Krzys zooms down a slide in Warsaw and shrieks with delight, paying no mind to the workmen who are busy demolishing the playground walls.
At first glance, there is nothing special about the old walls. But take a closer look and it becomes apparent that a couple of stones are inscribed with Hebrew.
The tombstones, known as Matzevot, from hundreds of Jewish cemeteries across Poland -- that were abandoned or destroyed following the Holocaust -- were used to pave roads and put up walls during the communist era.
It was part of an effort to rebuild a capital city that had been razed to the ground by Nazi Germany during World War II, a conflict that also all but wiped out Poland's Jewish community.At the small playground in Warsaw's Praga neighbourhood, the stones were used to build an arbour and the walls surrounding a nursery school as well as a dance floor.
Krzys's mother Kamila Zagorowska, who has been living in the neighbourhood for seven years, was surprised to hear the stones came from a Jewish cemetery.
"If that's the case, then the Matzevot should be returned to their place," said the 42-year-old mother of four.
- 'Horrific' desecration -
"And to think that people came here to dance, that they danced on graves," added Tadeusz Zbolimowski, 50, a driver and longtime Praga resident.
"They never should have been brought here."
Once removed, the stones are put on palettes and driven back to Warsaw's Jewish Brodno cemetery."The desecration that has taken place here in Poland over 50 years of the Germans and then the Soviets has been horrific on so many different levels," Poland's chief rabbi Michael Schudrich told AFP.
It's important "to undo the damage that was done during the double occupation of Poland from '39 to '89 by the German Nazis and Soviet Communists," he said, applauding the city for its work to return the Matzevot.
"We can't fix everything, but what we can, we should try to fix."
The war turned Warsaw into a pile of rubble. In 1945, building materials were in such short supply that bricks from the city of Wroclaw -- Germany's Breslau before the war -- were brought 370 kilometres (230 miles) to Warsaw to rebuild the capital. Matzevot tombstones became just another building material.
In one of the more shocking cases, a cowshed was built out of tombstones in the village of Parysow, near Warsaw.The stones were generally stacked in such a way as to hide the inscriptions and religious symbols, but there were exceptions.
Hebrew script is visible, for example, under the vine leaves covering the arbour at the Praga playground.
"Poland regained its independence 24 years ago. Today we can speak freely, even on issues as difficult as this one. No subject is taboo anymore," said district deputy mayor Jaroslaw Karcz.
"We can right the wrongs of history, and for that we have indispensable tools and financial resources at our disposal," he told AFP.
The city has earmarked 95,000 euros ($122,000) for the project.
"It's just the beginning of a long process, a very important one from the ethical point of view of Jews and Poles," said Warsaw Jewish community leader Anna Chipczynska.
"But all of this requires significant financial resources that we still need to find."
The "From The Depths" nonprofit, a joint US-Israeli-Polish organisation that is involved in the project, has tasked itself with creating digital archives of the Matzevot.
"Jews from all over the world come to Poland to trace their roots and find the graves of their ancestors. We want to help them," said Lena Klaudel, coordinator of the group's Matzeva Project, which they are carrying out with the help of the Norwegian University of Science and Technology.
But the tombstone operation has its critics.
"What's the good of destroying everything? The Hebrew is only on one of the arbour posts," said Jerzy Mickiewicz.
"Better for the stones to continue to serve the living," his wife added.
Those tombstone chunks are now being salvaged and returned to their cemeteries through a project meant to turn the page on a dark chapter in complex Jewish-Polish relations.