Jacob's Well is one of the most significant natural geologic treasures in the Texas Hill Country. It is one of the longest underwater caves in Texas and an artesian spring. Jacob’s Well surges up thousands of gallons of water per minute and acts as headwaters to the beautiful Cypress Creek that flows through Wimberley, sustaining Blue Hole and the Blanco River, recharging the Edwards Aquifer, and finally replenishing estuaries in the Gulf of Mexico.
The twelve foot (4 meters) diameter mouth of the spring serves as a popular swimming spot for the local land owners whose properties adjoin Cypress Creek. From the opening in the creek bed, Jacob's Well cave descends vertically for about thirty feet (10 meters), then continues downward at an angle through a series of silted chambers separated by narrow restrictions, finally reaching a depth of one hundred and twenty feet (40 meters). Until the modern era, the Trinity Aquifer-fed natural artesian springgushed water from the mouth of the cave, with a measured flow in 1924 of one hundred and seventy gallons per second (six hundred and forty liters per second) discharging six feet (2 meters) into the air. The spring is the greatest source of water recharging the Edwards Aquifer.