Where And What Is The Sounding Arch?

It is a railroad bridge, built in 1838 by Isambard Kingdom Brunel.  It was constructed for the Great Western Railway at Maidenhead.  The original bridge has arches with perfect echos, hence the name.  

The bridge also has the distinction of comprising the widest and flattest brick arches in the world.  The design inspired a few doubts at the time.  The bridge spans 128 feet but rises only 24 feet.  Some incorrectly predicted that it would be unable to take the weight of a steam engine.  Brunel cunningly put up false supports to placate those convinced that the arches could not take the weight of a train.  The fake supports washed away unexpectedly, proving that the original bridge was strong enough all along.

The original bridge was copied almost exactly, to build a second bridge to carry two more railway lines on the same section of track.  However, the newer/extended bridge lacks the spectacular acoustic qualities of the original Sounding Arch.