Esther 7:9-10

9One of the king's eunuchs, Harbona, said, ‘There is a wooden tower near Haman's home. It is 22 metres high. His men built it so that he could hang Mordecai on it. Mordecai is the man who saved the king's life.’ The king said, ‘Hang Haman on the tower until he is dead.’

10So they took Haman and they hanged him on the tower until he was dead. It was the same tower that Haman had wanted to kill Mordecai on. After that, the king did not feel so angry.