Holy city means sacred city.
The suffering of Jews stems from human sin, God's punishment and God's mercy.
The sin of Jews: disobedience to God and disowning Jesus;
God's punishment: God told Jews through Jewish prophets that he would punish them;
God's mercy: In suffering, Jews repent and return to their faith in God, thus avoiding ultimate destruction.
For example, it was precisely because the Jews suffered extremely in World War II that they won the sympathy of the whole world after the end of World War II and obtained the approval of the United Nations (the Soviet Union and the United States voted in favor at the same time, which was extremely rare at that time), which made the Jews successfully restore their country after losing their homeland in 2000, which was unique in human history.