The Danube Gorges is the natural border between Romania and Serbia, the place where the Danube passes through the Carpathian Mountains. It narrows to about 230 meters for 9 km. The maximum depth of the Danube is about 75 m.

Before the artificial lake (The Iron Gates) was built, Danube has created its own spectacle here: the Large Boiler and Small Boiler. The power of water created bubbles, which gave the impression of vortices, giving the sensation that the water is boiling. Therefore it is also known as The Danube Boilers.

The Big Boilers are 4 km long and are surrounded by the Ciucarul Mare (Romania) and Veliki Strbac (Serbia) mountains.