Nitra Castle is a city castle that over time changed due to many reconstructions of its design and fortification. It's still a functioning castle - it functions as a seat of Roman-Catholic Church. Therefore, you cannot visit the interior of the castle.
There is lot to see too, the castle grounds, the Cathedral of St. Emeram, the Diocese Museum, the Casemates and enjoy the highest point of the city - the Tower gallery.
Castle grounds open daily:
April - Sep: 6:00 am - 7:00 pm
Oct: 6:00 am - 7:00 pm
Nov - March: 7:00 am - 5:00 pm
Expositions - check official site.
Castle grounds: €0.50
Combined ticket - expositions:
Full: €2.00
Reduced: €1.00
Combined ticket + Tower:
Full: €4.00
Reduced: €2.00
Wikipedia https://en.wikipedia.org/wiki/Nitra_Castle
Official Website http://www.nitrianskyhrad.sk/en/
Address 1013 Námestie Jána Pavla II., Nitra 94901, Slovakia
Coordinates 48°19'5.297" N 18°5'12.327" E