Tintern Abbey was established on this date.

"Tintern Abbey was established on this date" -- May 9, 1131 -- "by the Anglo-Norman nobleman Walter de Clare on the Welsh side of the River Wye on lands given him by Henry  I." 

 From a brief notice in  Touchstone Magazine, which you can find here.

A fuller history is here on the inevitable Wikipedia, whence cometh indeed the illustration.  And note the wonderfully useful passive voice:  "The Abbey fell into ruin at the dissolution of the monasteries . . ."  What a co-incidence.  Just, sort of, happened.  No-one knows why.