Favourite Castles, Abbeys, Priories, and Friaries

Inspired by an off-the-cuff remark I made in another thread, I thought I would actually start this thread off.

Please share your favourite castle (or Mediaeval Abbey, Friary, or Priory), if possible with a picture and saying a little bit about it.

I will kick off with Corfe Castle.  A picturesque ruin in Dorset (belonging to the National Trust),  and as a bonus can be reached by steam train from Swanage with one of the finest 'railway views' in Britain!  A good view from the castle as well