Romance and political. Good acting, filmography and costumes.
Looking back at this now a while after watching it, I would say Joo Sang Wook as the older Prince Lee Kang left the strongest impression on me.

As a historical drama it isn’t super original, but it pretty much ticks off all the boxes, and does it quite well:

Some tense scenes, some emotional and tear-inducing scenes, and some scenes making you smile and laugh.

A few things, like close-ups of horse riding, could have been better, but it might also be due to the fact that the show is 6 years old at time of writing, so I’m expecting better per today’s standard.

As usual I don't really remember the music, so giving that an "average" score.