Answer:
Poland
Explanation:
If it's the castle I am thinking of, then it is Lapalice Castle, in Northern Poland, near the Baltic port city, Gdańsk. If I remember correctly, they never got the required permits, and construction came to a halt. They were going to demolish it, but that too would cost money, so they simply abandoned it. It still stands (I believe) but remains unsafe to explore. Then again I lack context of the question so it could be an entirely different castle.
