La Jonction is the confluence of the Rivers Rhône and Avre. The effect of the rivers mixing is quite striking due to their differing colours.
The picture above was taken from the Pont de la Jonction, a railway bridge that crosses the river just below the junction. This is the best place to view the feature from - the effect of the colours mixing can clearly be seen to the right as the Rhône (left) overpowers the Avre (right). A wall has also been constructed under the river, from the point to the bridge, to keep the waters separate for longer to enhance the effect. Then ubiquitous Mont Salève can be seen in the background.
The bridge itself is shown below. This picture was taken from the end of the point. From here, the colours are still fairly impressive, but are not as distinct as when seen from above.