Abbey Cwm Hir

There's not a lot left of Abbey Cwm Hir, the Cistercian Abbey which was the last resting place of Llewelyn ap Gruffydd, the last independent Prince of Wales.
His head, of course, was elsewhere. It had been taken to London to be exhibited on London Bridge.
Yesterday was the anniversary of the Prince's death, near Aberedw, on the banks of the River Wye, just outside Builth Wells. Builth had a fine big castle then - it was an important centre - and Llewelyn spent the night at the smaller castle at Aberedw (nothing much remains of that now). He was with a small party when they were attacked by English soldiers, and Llewelyn was killed by an English man-at-arms called Stephen of Frankton. He had been going to meet with local leaders, with a view to them joining his rebellion against Edward I, while his main army was just outside Builth. They were defending the Orewin Bridge across the River Wye - but the Marcher Lords managed to outflank them by using a nearby ford. It was a rout, and the last rebellion of the independent Welsh was all over bar the shouting.
Dafydd, Llewelyn's brother, held out for a little while longer, but he was finally captured and taken to Shrewsbury, where he was hanged, drawn and quartered - a style of execution which had never been used on a man of such high rank before, and which Edward I had personally insisted on. I think that's the worst part of it - Edward and Dafydd had grown up together, and played together as children, when Dafydd's father was held hostage in the Tower of London, and Edward was ruthless enough to do that to him.
Llewelyn's head was reputedly washed in the spring at Cilmeri, near the spot where he was killed, and there is now a memorial to him there. That's a very Welsh thing - the legends of Welsh saints are littered with people who have their heads cut off at holy springs - the most famous being St Winifred at Holywell, who was revived by her saintly uncle - and there are other, less Christian, legends like the story of Bran's miraculous head, which entertained his followers magically for years after it had been cut off, and was finally buried at the Tower of London to protect Britain from attack. Bran is also the Welsh word for raven, hence the legend that there must be ravens at the Tower of London, or there will be disaster.
The big standing stone can easily be seen from the main road, and there's a ceremony there every year to commemorate his death.