There are European castles from long periods of time and they do not look alike at in the medieval period. Most of the castles were fortresses, thick-walled behemoths, usually without luxuries such as plastered walls and finely attired spires and roofing patterns.
The most beautiful European castles are from the baroque times the 1600’s and 1700′ s, while later periods would erect truly sumptuous buildings in the middle of large cities that in nothing resemble what most people think as a castle. These are bigger than what you see in Game of Thrones, but have no fortress character at all.
The Red Keep
This is more or less realistic if you consider it to be a well defended palace than a traditional castle, since it’s taller and more delicate compared to a traditional castle. The outer walls look like they were added at a later date showing that the Keep expanded through the ages. This gives it more history I suppose and makes it more believable.
This is extremely realistic except for where it is located. It’s sprawling, not as tall, solid, and well fortified, all good. But it’s in the North. And the roofs of the towers are flat. They would cave in due to the weight of the snow that would pile up during the years long winter that happens from time to time. Typical castles in such locations have very steep roofs. That would be the one glaring issue.
Yeah, not happening. These towers, the ones on the right, should’ve collapsed long ago due to erosion. No way in hell can that keep standing for hundreds of years.
Again, nope. This is ridiculous. It would be ridiculous even if the mountain it’s built on had not been carved inside to create those pillars that support the castle.
Apart from the above, Casterly Rock is said to be built into a mountain, which, while not impossible, is improbable. There’s no reason to build a castle into a mountain when it’s infinitely easier to build on top of it.
To conclude, for it to be more parallel with real history, a lot more of the castles should have been smaller dirt-and-wood sort of deals, maintaining a super fortress every 50 km is not very easy or likely. Overall, Dragonstone might be the most realistic of them all, even if it’s far too close to the coast to not be affected by soil erosion.