A map of the watershed clearly shows the gap in the river where it flows underground.
It is generally thought that many years ago the river flowed underground, but over time the rock above the river disappeared, creating the current form of the canyon.
During exceptional drought large portions of this river may flow underground, with scattered pools of surface water.
And maybe, behind the thunder and in the roar of the waters flowing underground, you'll hear the laughter of dead kings.
The stream is to flow partially underground, partially above-ground and to discharge into the Dommel near the railway station.
It is thought that water flows underground from the southern Tibesti mountains and then emerges in these springs.
The valley has several stalactite caverns in the limestone, with some of the tributary streams flowing for considerable distances underground.
This is supposedly a measurement to the river level as it flows underground through a tunnel at the point it passes underneath the trestle.
More than 70 bridges were built over the stream, and in parts of the city centre it flows underground.
During much of its route it flows underground, beneath the city's infrastructure.
