What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora

What are/have been the most impregnable fortresses in history? - Quora

At what point in history were castles the best built and strongest? - Quora

What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora

How would you design the most impenetrable medieval fortress? - Quora

At what point in history were castles the best built and strongest? - Quora

What are some of the best fortified historical fortresses in your opinion? - Quora

What are/have been the most impregnable fortresses in history? - Quora

What is the most impressive, best designed medieval fortress in the world? - Quora

What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora

What are/have been the most impregnable fortresses in history? - Quora

What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora

What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora

What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora

Why did the French build forts? - Quora

What are some of the greatest fortresses ever built (they have been successful in repelling invaders and/or are impressive in terms of their size and ingenuity)? - Quora