Nothing is known about its actual layout, precisely because the design of a place made up of secret routes to protect Castruccio from all dangers had been shrouded in absolute secrecy. It was discovered that the fortress had been surrounded by a series of accesses connected to one another so that if the enemy passed unscathed through the first, he would find it difficult to pass through the other two; meanwhile Castruccio would have been able to escape easily through the close network of tunnels, prepared precisely in case of danger, provided with niches to hold torches to light the way.
