I don’t think that there is a worst nightmare that being permanently locked up, alone and having your thoughts torturing yourself day and night.
If you go to San Francisco, California it is a must to go to Alcatraz. There is so much history in there, not only for the time that was served as a federal prison, but it was a military fortification and military prison as well. Also for a period of time ( 19 months) it was occupied by Native Americans from San Francisco who were part of a wave of Native American Activist across the U.S. Go visit to learn more. 🙂