Palazzo Caetani is crossed by a network of caves that go down to about 15 meters deep to unknown destinations. A legend has it that the Emperor Nero would use these to supply water to his imposing villa of Neptune. The Caetani used them as walkways between the different properties to secure their escape in case of danger. During World War II the citizens of Cisterna found refuge for 58 days. There is access by a spiral staircase in the courtyard of Palazzo Caetani.