I had never eaten breakfast in a castle -- well, cross that off my list! I enjoyed a traditional Welsh breakfast in Cardiff Castle while listening to melodic harp and guitar music in addition to Welsh folk songs. I also toured the medieval Gothic Cardiff Castle complex that was built in the 11th century. My second photo shows the 'arrow-loops' or 'arrow-slits' in the castle. They are narrow openings or crosses set inside walls and towers enabling defenders to launch arrows at potential invaders or attackers. It's hard to wrap your head around that concept in 2019...
Cardiff Castle is rented out for parties, weddings and even as a filming location, in addition to the tour revenue. This helps defray the cost of castle upkeep. So I guess you'd call it a "working" castle.
The last photo is of the Cardiff waterfront. While at Cardiff Bay I also saw the Senedd - the National Assembly for Wales, the Wales Millennium Centre, and the Pierhead Building. A carnival was in full-swing at the waterfront, so there was music and activity well into the evening.