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3 Days in Dublin - Things to Do in Dublin
"You don’t have to go far to see a castle, as the Dublin Castle is in the heart of Dublin. It played a massive role in Ireland’s history, as it was the seat of England from 1204 until 1922. While no one lives there now, you can walk inside to see the how the staterooms used to be. There are over 11 acres to explore, including multiple museums and gardens."