In Lviv, a hidden work by a master is discovered.

LVIV, Ukraine — For years, no one paid attention to the side wall of the former St. Mary Magdalene Catholic church in Lviv. It was, after all, the location of the toilets, where stained tiles covered layers of mold-encrusted plaster and paint from a Soviet renovation in the 1960s.

But four years ago, the new management of a cultural center in what had been the church went looking in the midst of their own renovations for a rumored hidden artwork. After dismantling the restrooms and painstakingly removing layers of paint and plaster, a scarred, century-old masterpiece began to emerge — a dramatic mural by the Polish artist Jan Henryk de Rosen.

“This beautiful masterpiece was hidden for many, many decades,” said Teras Demko, co-director of the Organ Hall, which has a concert hall for organ, chamber and symphonic music along with an art gallery. “During the Soviet regime, they tried to hide all mentions of anything connected to the sacred world.”

The coronavirus pandemic limited attendance, and the Russian invasion forced the center to close briefly. Its reopening amid the arrival of tens of thousands of people fleeing the hard-hit east to this relatively safe western city is giving the rediscovered mural a whole new audience. The Organ Hall is offering free or discounted tickets to provide “a portion of normal life” in the middle of the war, Mr. Demko said.

De Rosen used pigment mixed with beeswax thinned with alcohol for his works. In this one, painted in the late 1920s or early 1930s, a stylized Jesus is baptized by Saint John while other disciples watch from shore.

A white line runs through the middle of the mural where the men’s and women’s restrooms were separated by a partition, destroying part of the work. But traces of de Rosen’s typically expressive faces, painted from real-life models and his sinuous lines depicting the Jordan River remain, and the gold leaf surrounding the mural and decorating the vaulted ceiling still gleams.

The church was originally constructed on the site of a 17th century one, later destroyed and then renovated in the early 1920s. In the 1960s, when what is now Ukraine was part of the officially atheist Soviet Union, the church was one of thousands closed down.

De Rosen, who died in the United States in 1982, was one of the most prominent 20th century painters in the world of religious art. He was commissioned to paint murals at the papal summer residence in Italy and did dramatic frescoes with art nouveau influences that cover the interior of the Armenian cathedral in Lviv.

De Rosen, a World War I veteran who served as a translator at the Versailles peace conference, emigrated to the United States in 1939 when war broke out again

In the United States, he taught art at the Catholic University of America in Washington, D.C. Among other works, he painted the murals in San Francisco’s Grace Cathedral. His ceiling mosaic in Washington’s Basilica of the National Shrine of the Immaculate Conception is considered one of the largest of its kind in the world.

Mr. Demko said the cultural center has no plans to restore the mural to its original vivid colors. He said it was a reminder of Russia’s past attempts to erase Ukraine’s heritage and its current effort to do it again.

“This place doesn’t serve a sacred function, so it doesn’t need to be painted like an icon,” he said. “It should tell the story so it doesn’t happen again.”