South Stack (Welsh: Ynys Lawd) is an island situated just off Holy Island on the North West coast of Anglesey. It is famous as the location of one of Wales' most spectacular lighthouses.
It has been a warning beacon of the treacherous rocks below, for passing ships since its completion in 1809. The 28 m (91ft) lighthouse was designed by Daniel Alexander and the main light is visible to passing vessels for 28 miles, and was designed to allow safe passage for ships on the treacherous Dublin - Holyhead - Liverpool sea route. It provides the first beacon along the northern coast of Anglesey for east-bound ships. It is followed by lighthouses, fog horns and other markers at North Stack, Holyhead breakwater, The Skerries, the Mice and at the north-east tip of the island Trwyn-Du. The lighthouse is operated remotely by Trinity House.
Until 1828 when an iron suspension bridge was built, the only means of crossing the deep water channel on to the island was in a basket which was suspended on a hemp cable. The suspension bridge was replaced in 1964, but by 1983 the bridge had to be closed to the public, due to safety reasons. A new aluminium bridge was built and the lighthouse was reopened for public visits in 1997. Thousands of people flock to the lighthouse every year, thanks to the continued public transport service from Holyhead's town centre.
There are over 400 stone steps down to the footbridge (and not, as local legend suggests, 365), and the descent and ascent provide an opportunity to see some of the 4,000 nesting birds that line the cliffs during the breeding season. The cliffs are part of the RSPB South Stack Cliffs bird reserve, based at Ellin's Tower.