Pontcysyllte Aqueduct

The Pontcysyllte Aqueduct () is a canal aqueduct in north east Wales. It took 10 years to design and build. It was completed in 1805. It is the longest aqueduct in Great Britain, and is the highest canal aqueduct in the world. The 18-arched stone and cast iron structure is designed for narrowboats.
The aqueduct was part of a grand plan which was never completed. It was part of the proposed Ellesmere Canal. It would have been an industrial waterway which made a link between the River Severn at Shrewsbury and the port of Liverpool on the River Mersey. 
The westerly high-ground route across the Vale of Llangollen was chosen. A less expensive route was surveyed to the east, but the route chosen would have taken the canal through a mineral-rich area. It would have taken the canal through the coalfields of North-East Wales. However, only parts of the canal route were completed. The plan fell through because the money ran out. The capitalist system at the time was primitive and unreliable. Most major work on the canal stopped after the completion of the Pontcysyllte Aqueduct in 1805.
The structure is a Grade I listed building. It is recognised as a UNESCO World Heritage Site.
Name.
The name "Pontcysyllte" is Welsh for "Cysyllte Bridge", or "Bridge of Cysyllte". Cysyllte is the township of the old parish of Llangollen, where the southern end of the bridge lies. 
World Heritage Site.
In 1999, the aqueduct and its surrounding lands were submitted to the "tentative list" of properties being considered for UNESCO World Heritage Site status. The aqueduct was suggested as a contender in 2005, its 200th anniversary year. It was finally announced in 2006 that a larger proposal, which covers a section of the canal from the aqueduct to Horseshoe Falls would be the United Kingdom's 2008 nomination.
Parts of the site including the length of canal from Rhoswiel, Shropshire, to the Horseshoe Falls, Pontcysyllte Aqueduct, and Chirk Aqueduct were visited by inspectors from UNESCO in October 2008. It was carried out to analyse and confirm the site management and authenticity. The aqueduct was named by UNESCO on the World Heritage List on 27 June 2009.