castle destruction and reconstruction.

Ladies and gentlemen. I have a question about Heroes 3.5. It states that you can build and destroy castles. I understand how to destroy them, but when I destroy a castle completely, I am kicked out, and the castle becomes inactive. Question: How do I build another town? In other words, as I understand it, you can demolish a town, say, of Haven, and build a Necropolis town instead. How do I do that? Does anyone know?