Jones Falls Dam, Stone arch dam and lock system in Rideau Lakes, Ontario, Canada.

Jones Falls Dam is a stone arch dam on the Rideau Canal in Rideau Lakes, Ontario, built 1828–1831. Its Potsdam sandstone masonry is 17.3 m high from the bedrock foundation, 8.2 m thick at the base and 3.7 m at the top, with an earthen berm adding about 1.2 m. In front of the dressed stones lies a 1.5 m layer of grouted broken stone, used because suitable clay ran out; the apron extends about 50 m.

This structure was completed in 1831 as the highest dam in North America at that time, built over several years under British Royal Engineers. Its construction represented a major engineering achievement for the early 19th century waterway development.

The dam's stone face carries the nickname Whispering Dam: a person speaking at normal volume at one end can be heard at the other, because sound travels along the curved masonry. The stones still show the dimples left by the large timber tongs used to lift them into place.

The dam sits at the head of a bedrock canyon partway up the former rapids, with the locks alongside it. A road built in 1827 from the Elgin quarry to Jones Falls served the stone hauling and remains the approach route. Visitors walk between the dam crest and the lock chambers; the arch face and the tong dimples in the stones are seen on foot.

The stone construction creates surprising sound effects where voices and noises echo along the surface, producing an unusual acoustic property of the structure. Many visitors discover this phenomenon unexpectedly while walking across the dam.