AMSTERDAM, Netherlands — The old chestnut tree visible from Anne Frank’s attic window that comforted the Jewish teenager as she hid during the Nazi occupation of the Netherlands is rotten and must be cut down, the City Council said yesterday.

The tree in the courtyard behind the canal-side warehouse where the Frank family took refuge for more than two years has been attacked by an aggressive fungus and a moth, called the horse chestnut leaf miner, the council said.

The tree’s condition has rapidly deteriorated in recent years, the city said. The inner wood is rotten, and the dying roots and bark are not regenerating. Experts estimate the tree’s age at 150–170 years.

The Anne Frank House Museum, where the tiny apartment has been preserved, said grafts and a sapling from the original chestnut have been taken and that it hopes to replace the once-towering tree with its progeny.

“It’s very sad, but the decision has been taken,” a museum spokeswoman Patricia Bosboom said.

The chestnut is familiar to readers of “The Diary of Anne Frank.” She often longingly regarded the tree from inside the attic, which had the only window not blacked out to prevent outsiders from seeing movement inside the apartment on Prinsengracht Street where the family hid.

The Jewish teenager made references to it in the diary that she kept in the 25 months she remained indoors until the family was arrested in August 1944.

“Nearly every morning I go to the attic to blow the stuffy air out of my lungs,” she wrote on February 23, 1944. “From my favorite spot on the floor, I look up at the blue sky and the bare chestnut tree, on whose branches little raindrops shine, appearing like silver, and at the seagulls and other birds as they glide on the wind. …As long as this exists, I thought, and I may live to see it, this sunshine, the cloudless skies, while this lasts, I cannot be unhappy.”

Frank died of typhus in the Bergen-Belsen concentration camp in 1945.