Warsaw, Poland ? The International Auschwitz Council agreed Tuesday to modernize a 51-year-old exhibition at the site of the Nazi death camp and build walls to prevent the ruins of gas chambers from sinking into the ground.

The decision to renovate and preserve remains of the vast Nazi death camp in southern Poland marks a change in the long-standing approach to maintaining the site, which has been left as the Allies found it when they liberated the camp at the end of World War II.

But two of the gas chambers are slowly sinking into the ground and will likely slide out of sight within the next two decades if nothing is done. How to save them prompted debate on the council, with a majority favoring a Polish expert’s proposal to halt the erosion by building walls sunk into the ground on either side of the slipping chambers.

“We have to preserve without reconstruction,” said Piotr Cywinski, the new director of the Auschwitz-Birkenau Memorial and Museum. He warned that doing nothing is tantamount to letting history slip away: “We must decide to do this if we want to be able to see these gas chambers in 20 years.”

The council also backed a proposal to renovate an aging exhibition dating back to the early years of communist rule in Poland.

Cywinski said the exhibition, in austere barracks at the sprawling complex, has become old-fashioned compared to modern museums like Yad Vashem in Israel and the United States Holocaust Memorial Museum in Washington.

It is “the oldest exhibition about the Shoah (Holocaust) in the world,” Cywinski said on the sidelines of the daylong council meeting in Warsaw. “We really must change.”

Some Holocaust survivors in Israel fear modernization could make the camp seem more like a museum and damage the somberness of the site where nearly 1.5 million people, most of them Jews, were slaughtered by the Nazis.

Cywinski said no changes would be made to the remaining crematoria, barracks and watchtowers, and he pledged to keep the powerful exhibits of hair, glasses and other personal belongings that were stripped from victims.