4. Highgarden
The seat of House Tyrell and regional capital of The Reach is said to be among the most attractive of the great castles of Westeros. Its grandeur is well renowned, particularly for its huge gardens and strong tiered walls. It is described as a vibrant commerce of the arts, and his home to many kinds of musicians and diligent craftsmen. There may actually be activity here beyond the abundance of wh*ring and fighting! The Tyrells are the second wealthiest house in Westeros, and as well as holding honour and chivalry in high regard, they are also a flowery bunch who like to indulge in extravagance. You can imagine their castle will be full of colourful gardens and tasteful architecture, pertaining to an almost fairy-tale like palace. Of course, this is Martin's world, so I'm quite sure that no such thing exists, but it may be the closest thing. It certainly sounds like it would be far more aesthetically pleasing to the slums of King's Landing, or the grey dreariness of Winterfell. Its geographical location also serves it well the Reach is the most fertile land of Westeros, and the castle itself is located on the banks of the River Mander. I'm sure this would make for a beautiful setting on screen, and with the Tyrells and Highgarden being of such significance to the world, I would be very surprised if we were not taken there.