By car:

From the airport: Take the M1 Motorway southbound towards the City Centre. Once on Dorset Street, continue on straight to Bolton Street. Turn left onto Capel Street and continue on straight to the river. Turn left onto Ormond Quay and then take the next turn right, traveling over O’Connell Bridge onto D’Olier Street.
Trinity College will be directly ahead. Bear right at the traffic lights, keeping the College on your left. Bear Left, to travel along Nassau Street in the direction of Merrion Square. Turn right onto Merrion Square West.
The Merrion is situated at the top of Upper Merrion Street on the left hand side, beyond Government Buildings, which are on the right hand side.