These are the ruins of Melrose Abbey in the Scottish Borders, founded by Cistercian monks in 1136, and now maintained by Historic Scotland. Alexander II and other Scottish kings and nobles are buried at the abbey and the embalmed heart of Robert the Bruce is said to be buried here. We visited it on a sunny April day last year.
Below is a view from the roof:
and here is a close up of two of the gargoyles: