I've been to Enniskillen dozens of times (it's my mum's hometown) but had not actually, as far as I remember, ever gone into the castle. The famous front, called the Watergate, dates from the early 1600s.
The county museum was closed for refurbishment when we went but there was a small display on the fascinating Maguire clan, who ruled the area for about 300 years. Also open was the excellent Inniskillings Museum, which has a detailed, interesting and often moving amount of the eponymous regiments (in one of which my father did his national service in the early 1950s!). Outside there are some military vehicles in display, nicely positioned in the barracks.
I'd appreciate the museum asking families to keep children under control, because their incessant yelling (and these kids were approx 11-12 years old) really ruined a lot the experience/ability to read. Also appreciated would be some kind of disabled access, my dad struggled with the 2 flights of stairs.
Very much worth a visit on any trip to Enniskillen. read more