The River Liffy.

The Liffey is about 80 km (50 mi) long, it .rises in the Wicklow mountains at a height of about 518 m (1,700 ft) above sea level in northern County Wicklow. It flows generally north-east before entering Pollaphuca reservoir. This reservoir supplies water to Dublin about 20 km (12 mi) to the north. The dam also has a hydroelectric plant.

It then flows on into County Kildare before turning east into Dublin and Dublin Bay, where it discharges into the Irish Sea. The Liffey is tidal in its lower course, but is navigable only as far as the first of Dublin's ten bridges.

On its way it is crossed by the Grand Canal, which links Dublin to the River Shannon.