People tend to check in during these times:
More of a Fort than a castle
It's sort of like the Gravensteen in Ghent. #VisitFlanders
Designed by Lieutenant Colonel Jonathan Williams it was constructed of sandstone with walls measuring 8 feet thick at the base. The castle was designated a City landmark in 1967.
Every hour (on the half hour) go to the Ranger table for tickets to the rooftop tour (which will be an hour later but there is plenty to do) on the weekend. It's worth it for the views of NYC.