The old chestnut tree visible from Anne Frank’s attic window in Amsterdam that comforted her as she hid from the Nazis from 1942 to 1944 is diseased and rotten and must be cut down, the city council said. Experts estimate the tree’s age at 150 to 170 years. The Anne Frank House Museum, where the tiny apartment has been preserved, said that grafts had been taken from the chestnut and that it hoped to replace it. Anne Frank made several references to it in her diary. “Nearly every morning I go to the attic to blow the stuffy air out of my lungs,” she wrote on Feb. 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.”