On which river is this section called the "Iron Gates" located?

The picture is from the Danube river. It is from a section of the river known as the "Iron Gates". The Iron Gates of the Danube River originally consisted of four narrow gorges and three wide basins spread over several miles of the river dividing Romania and Serbia. Some people consider the entire 83-mile stretch of the river to be the Iron Gates, but most define it as just the section with the four narrow gorges. The term "Iron Gate" was first used by The Times of London in an 1853 article about this section of the river.

The rock sculpture is of Decebalus, the last king of Dacia, who fought against the Roman emperors Domitian and Trajan to preserve the independence of his country, which corresponded to modern Romania. It is a 42.9 m height and 31.6 m width carving in rock of the face of Decebalus. The sculpture was made between 1994 and 2004. It was made by Drăgan. It is located near the city of Orșova in Romania.

It is the tallest rock sculpture in Europe.