At the foot of the main Caucasus range, beneath a field of lava boulders, a group of powerful springs issues from Upper Jurassic carbonate flysch; researchers have named it the "Narzan-Vaucluse". The spring yields 25–30 million liters of hydrocarbonate-calcium water a day, equivalent to 300–350 l/s. From it rises a river that flows through the village of Keterisi, where a cascade of mills is set up on the mineral water.