These plain stairs were replaced by the modern Grand Staircase. The second-floor balcony is accessed by an ornate walnut spiral staircase. The house has kept its original staircase, flooring and paneled walls. The area around the entrance to the Grand Staircase was also damaged. A hidden door leads to a narrow staircase. It gets its name from the stone spiral staircase inside. The cells next to the portal feature staircase leading to the roof. The area around the top of the basement staircase was heavily bloodstained. It contains a spiral staircase of 379 steps. This right angle forces the steps into a shape resembling a staircase. An inscription commemorates this above the door to Staircase IV. A transition space was built between rooms located on either side of the main staircase. Giambattista Castello designed the magnificent main staircase. The return trip down is by way of the same circular staircase. A mono string staircase is a term used for a steel spine staircase with treads.