Albert Barnes Commentary 2 Samuel 17:23

"And when Ahithophel saw that his counsel was not followed, he saddled his ass, and arose, and gat him home, unto his city, and set his house in order, and hanged himself; and he died, and was buried in the sepulchre of his father." — 2 Samuel 17:23 (ASV)

To his city — To Giloh. Ahithophel was likely motivated by deep humiliation at the slight of his counsel being rejected. He is a memorable example of the impotence of worldly wisdom.