Today is St David’s Dsy, the feast of the patron saint of Wales.
Wikipedia has a quite detailed account of his life and legacy at Saint David and Historic UK also has a useful piece about him at St David, the patron saint of Wales.
There is more about the cathedral and the Saints and shrines associated with it and good photographs at St David's Cathedral | History and Photos
At first sight it is difficult to see much immediately other than the cathedral at St Davids which links to his medieval cult, but that clearly was important. St David’s Cathedral website has a useful introduction to medieval devotion to him which can be seen at
Much has been destroyed, and I do not know of a surviving medieval image of him as opposed to nineteenth and twentieth century church art.
In 2012 his shrine on the north side of the choir of St Davids Cathedral was restored and dedicated. There is an account of it on the cathedral website at St David's Shrine
Images: Feast, Fasts, Saints and the Medieval Church
Given that Pembrokeshire faces Ireland it is perhaps not that surprising that devotion to him crossed the Irish Sea. This was an important sea route in the middle ages and used by Strongbow, King Henry II and King Richard II on their journeys to Ireland. This Irish connection is brought out alongside evidence for Welsh pilgrims to St Non’s Chapel, the cliff top oratory named in honour of his mother and the traditional site of his birth and the adjacent holy well in Medieval pilgrimage to St Davids
St David’s Well in Co Wexford shows how the cult crossed the sea and it is described on two sites, at Saint David’s Well, Ballynaslaney
and at St David’s well Olygate
St David, Pray for us