Most of Ireland's tunnels date from the 19th century in the building of the railways, typically excavated through rock by blasting and then hand excavation.
The more modern tunnels include the longer road tunnels and utility tunnels, constructed from approximately 1940 to date, using a variety of tunnelling methods.
Historically, a number of country estates had tunnels, both to provide privacy (and means of escape) and to keep the views from the house clear of servants and labourers. Stone and brick built sewers are often mistaken for "tunnels", in particular in central Dublin.
There are a number of pseudo tunnels. For example, at Dunkettle in Cork, to construct the interchange at the north end of the Jack Lynch Tunnel, a section of railway approximately 100 m long was covered so that the N25 (now part of the M8) could cross the railway at a shallow angle - a "cover only" tunnel. Where the North Dublin Link Railway (Great Southern & Western Railway) passes under the Royal Canal and the Liffey Line (Midland and Great Western Railway), the railway is in essence in two cut-and-cover tunnels.
Railway
Operational
Bray Head Tunnel No. 1 (Connolly Station, Dublin to Rosslare Europort - 274 metres)
Bray Head Tunnel No. 2 (Connolly Station, Dublin to Rosslare Europort - 131 metres)
Bray Head Tunnel No. 3 (Connolly Station, Dublin to Rosslare Europort - 192 metres)
Bray Head Tunnel No. 4 (Connolly Station, Dublin to Rosslare Europort - 991 metres)
Cork, Albert Quay. (Cork to Bandon -?? meters))Demolished. aka High street tunnel.
Cork, Passage West Tunnel (Cork to Crosshaven - 520 metres)
Corrib Tunnel, Aghoose - Glenagad Co. Mayo. Built for the housing of the offshore Corrib gas pipeline and associated services, backfilled upon completion, ran a locomotive on narrow gauge track, (4,900 meters)
Gogginshill (Ballinhassig) (Cork to Bandon - 828 metres)
Ballymore Lower, Donegal (access tunnel to house) - On N56 near Dunfanaghy
James Street, Dublin (pedestrian tunnel connecting Guinness plant on either side of street)
Lough Key Forest Park (tunnel previously part of landed estate)
Esso N4 at Mullingar (Formerly Hamills), tunnel links two service stations either side of the dual carriageway, now closed due to lack of planning permission.
Crumlin Road, Belfast (Victorian era foot tunnel between Crumlin Road Gaol & the Crumlin Road Courthouse, formerly used by prisoners and staff)
