[3] The aqueduct, which was started in 1896 and opened in 1906, crosses several valleys and features numerous brick tunnels, pipelines, and valve houses.

[4] Work to build the Elan Valley reservoirs was undertaken because the rapid growth of the industrial city of Birmingham in the late 19th century had led to a lack of available clean water.

Thousands of navvies (workers) and their families lived in the purpose-built Elan Village during the construction of the first four dams at the turn of the 20th century.

The city's expansion resulted in regular outbreaks of water-borne diseases and major epidemics such as typhoid, cholera and dysentery due to the lack of clean water.

Victorian politician Joseph Chamberlain, the leader of Birmingham City Council, began a campaign to get clean water from the Elan and Claerwen valleys in mid Wales.

Due to the height above sea level of the Elan Valley, water would be fed to Birmingham along a 116-kilometre (72 mi) pipeline that employed a gravity feed with a gradient of 1 in 2,300.

This depot included a cement cooling shed, general stores, coal storage, workshops for carpenters, smiths, fitters and wagon builders, and sawmills.

The railway was required because the core of the Caban-coch, Pen-y-garreg and Craig-goch dams were built from large irregular stone blocks ("plums") embedded in concrete.

During the ten-year project to build the Elan Valley dams, the navvies lived in a village of wooden huts near the site.

[11][12][13] The project to supply water to Birmingham was officially opened by King Edward VII and Queen Alexandra on 21 July 1904.

A scale model of the reservoir network, in the form of ornamental ponds, is located in Cannon Hill Park in Birmingham.

The test proved successful as a significant breach in the middle of the 11-metre (36 ft) dam wall was caused by a charge placed at its base.

After the Dam Busters raid, steel cables were strung across the valley above the Caban-coch reservoir as a precautionary measure against German reprisals.

This scheme would have created a huge reservoir dwarfing all others in Mid Wales, and flooding miles of wild upland valleys.

The proposals were eventually abandoned in the face of reducing projections for industrial water demand and an increasing awareness of the environmental issues that such an expansion might create.