The Glynallen Mansion
Not all dungeons were hidden amenities. New York businessman George Marshall Alan built a 32,000 square foot mansion named Glynallen in 1917 and placed the property on the New Jersey landscape. Because he loved English architecture, Allen modeled the plans after an old castle that was equipped with a 10-foot high dungeon.
He wanted it to look a certain way. According to the Wall Street Journal, it was built to look 400 years old, and it has hosted plays in its dungeon, which has also served as the setting for a 1919 silent film. Glynallen was placed on the National Register of Historic Places in 1987. It is now permanently closed.