Albert Barnes Commentary 1 Samuel 19:22

"Then went he also to Ramah, and came to the great well that is in Secu: and he asked and said, Where are Samuel and David? And one said, Behold, they are at Naioth in Ramah." — 1 Samuel 19:22 (ASV)

To a great well — This refers to a large, well-known cistern at Sechu, whose site is uncertain, which Saul passed on his way from Gibeah to Ramah.