It is now a major government complex and a key tourist attraction. Dublin Castle have notified us that they offer free admission for visitors with special needs and their carers.
A bit about the history of Dublin Castle below:
Erected in the early thirteenth century on the site of a Viking settlement, Dublin Castle served for centuries as the headquarters of English, and later British, administration in Ireland. In 1922, following Ireland’s independence, Dublin Castle was handed over to the new Irish government.