The Nahal Zin is 75 miles (120 km) long and drains 600 square miles (1550 sq km). It is the largest wadi that begins in the Negev. The Nahal Zin was created by reverse erosion as the great height difference between the Negev Highlands and the Jordan Rift caused the underlayers to erode during the rainy season, resulting in the collapse of the harder strata of rock above. The landscape is mostly Eocene limestone, consisting of some brown-black layers of low-grade flint. The flint slows down the erosion of the limestone.

The Nahal Zin was the southern border of the land of Canaan that was promised to the Israelites. Numbers 34:3-4 (KJV): “Then your south quarter shall be from the wilderness of Zin along by the coast of Edom, and your south border shall be the outmost coast of the salt sea eastward: And your border shall turn from the south to the ascent of Akrabbim, and pass on to Zin: and the going forth thereof shall be from the south to Kadeshbarnea, and shall go on to Hazaraddar, and pass on to Azmon.”

Ein Avdat emerges at the base of the 50 foot (15 m) waterfall. This spring water is a bit salty, but the plants around the pool can survive on saltwater. The springs in this canyon are a geological puzzle. To this day, scholars don’t know where they come from. This is a dry region and during rainfall, the runoff doesn’t penetrate the ground but drains off in the wadis. The current theory is that the springs come from flash flood water that seeps down through the stream bed gravel and thus into the ground below.

Some caves carved into the chalky limestone cliffs of Nahal Zin were apparently used in the 6th century AD by monks from nearby Avdat. These monks sculpted out closets, shelves, benches, stairs, and water systems. A Greek inscription was found in one of the caves. It is a prayer to St. Theodorus, a monk whose name is also found in a monastery in Avdat. At the top of the canyon are the remains of a Roman fortress.