Dublin Castle. Wrapped up in this medieval stone fortification is the story of Dublin. For over 800 years Dublin Castle has been at the heart of Irish history and stood witness to some of the most pivotal events in our history. Built in the 13th century on the site of a Viking settlement it functioned as a military fortress, a prison, courts of law, treasury and the seat of English Administration in Ireland for 700 years. The castle was one of the main targets in the Easter Rising of 1916. It was ceremonially handed over to the newly formed Provisional Government and its leader Michael Collins in 1922. It is now used for important State receptions.