The Menai Suspension Bridge, built in 1826 by Thomas Telford, at sunset with snow covered mountains of Snowdonia in background

The Menai Suspension Bridge (Welsh: Pont Grog y Borth) is a suspension bridge between the island of Anglesey and the mainland of Wales. Designed by Thomas Telford and completed in 1826, it was the first modern suspension bridge in the world. Here shown at sunset in winter, with the mountains behind covered in snowfall. Before the bridge was completed in 1826, the island had no fixed connection to the mainland and all movements to and from Anglesey were by ferry (or, with difficulty, on foot at low tide). The main source of income on Anglesey was from the sale of cattle, and to move them to the markets of the inland counties or London, they had to be driven into the water and swum across the Menai Straits. The Act of Union 1800 increased the need for transport to Ireland, and with Holyhead as one of the principal terminals to Dublin it was decided to build a bridge. Thomas Telford was assigned the task of improving the route from London to Holyhead, and one of the key improvements was his design of the suspension bridge over the Menai Strait between a point near Bangor on the mainland and the village of Porthaethwy (which is now also known as Menai Bridge) on Anglesey. The design of the bridge had to allow for Royal Navy sailing ships 100 feet (30 m) tall to pass under the deck at high tide, and no scaffolding was allowed during construction as that would have violated the rule. Construction of the bridge began in 1819 with the towers on either side of the strait. These were constructed from Penmon limestone and were hollow with internal cross-walls. Then came the sixteen huge chain cables, each made of 935 iron bars that support the 176-metre (577 ft) span. To avoid rusting between manufacture and use, the iron was soaked in linseed oil and later painted. The suspending power of the chains was calculated at 2, 016 tons and the total weight of each chain was 121 tons. The bridge was opened to much fanfare on 30 January 1826.