The Phoenix Park tunnel, which was built in 1877 by the Great Southern and Western Railway, runs for half a mile beneath the green pastures of the park.
Starting at the Islandbridge Junction and finishing up close to the junction of the Cabra and Navan Road, the tunnel was originally used to provide a link to other big railway companies of the time, such as the Great Northern Railway of Ireland. The tunnel was mostly used to transfer goods, cattle and mail and was opened to passenger trains in 1901.
However, because there were sometimes only two passengers on any of the seven trains per day, which ran between Kingsbridge and Amiens Street (now Connolly), the passenger service was withdrawn completely in 1907.
There are recent proposals to reopen the trains to commuters over the next five years. This would allow some commuter trains to bypass Heuston Station and head for Connolly Station, via a loop through Cabra, as well as improving rail commuter services from Kildare, the west and southwest of the city.