The Bank of Ireland in College Green, opposite the main entrance to Trinity College, used to be the original Irish Parliament Building. It was built in 1729 according to plans by Sir Edward Lovett. When the Irish parliament, however, voted itself out of existence at the start of the 19th century (the Act of Union), the building was flogged off to the Bank of Ireland.
Enjoy the building from the outside first, it is regarded as one of Dublin's finest. Then head for the customer area (it is a working bank branch after all) and you'll be in the old House of Commons. Never has entry to an parliament been so easy.
Notice the small cannons outside the entrance ... these are real. The Bank of Ireland used to have its own militia.

