"Symphony of Stones" or "Basalt Organ" is one of the most famous and impressive natural monuments of Armenia. It is located in Garni Gorge, on the right bank of Azat river.

The monument is made up of thousands of columnar basalts stuck together up to 100 meters high. In its appearance it resembles an organ musical instrument, and therefore received the official name "Basalt Organ". However, it is better known as "Symphony of Stones".

The huge rock mass has a volcanic origin and was formed as a result of powerful lava. Due to slow cooling, the lower parts of the lava flows took the form of pentahedral and hexagonal columns.

The "Unknown Cave" nature monument is located in close proximity to the Symphony of Stones, and opposite, on the left bank of the Azat River, the Khosrov Forest State Reserve begins. The banks of the river are connected by the medieval bridge of Garni.