Author and historian Dan Jones traces 3,000 years of fortifications in "Castles," from Fort Sumter and Fort Pulaski to the Tower of London's gruesome dark history.
https://www.foxnews.com/travel/americas-little-known-castles-displaying-raw-power-hiding-plain-sight
https://www.foxnews.com/travel/americas-little-known-castles-displaying-raw-power-hiding-plain-sight