County Dublin (Contae Bhaile Átha Cliath) is a historic county surrounding Dublin city in the Republic of Ireland, with a population of 1,135,402 in 2016. It was abolished as an administrative or political unit in 1994, with its territory allocated to four new entities. Nevertheless it still coheres as a destination for travellers, in two ways: for the city to escape to the surrounds, for instance to the seaside at Howth or the races at Leopardstown; and for visitors to stay here and day-trip into Dublin while avoiding the city's congestion and high prices.
The former county now comprises the City of Dublin, the County of Fingal to the north, South County to the southwest, and Dún Laoghaire-Rathdown County on the south coast.
County Fingal lies to the north of the city.
South County is actually to the southwest; it's modern commuterland (eg around Tallaght) and lacks historic townships and visitor attractions.
Dún Laoghaire-Rathdown County to the south has:
Bray is just across the boundary in County Wicklow, but within the city's transport system.
County Dublin was at the centre of the historic Gaelic kingdom of Leinster, but its rivers, beaches and fertile hinterland attracted a series of visitors. The Vikings established a large settlement by what is now Dublin castle, on friendly terms with the Leinster kings, but their power was broken by the Munster man Brian Boru at the Battle of Clontarf in 1014. Next came the Normans, colonising the southwest and Leinster from the 12th century, and dividing the country into shires or counties. The Normans weakened in the 13th / 14th century and were ousted by the Gaels from much of Ireland, but they hung on in the area around Dublin behind their protective "Pale" - a palisade. The 16th century Tudors set about subduing the rest of the country, but "the Pale" had remained loyal and didn't suffer punitive wars. Dublin also fell swiftly to Cromwell so his atrocities were elsewhere, and King William marched in unopposed after the Battle of the Boyne. The county's fortunes rose and fell with that of the city, which became merely a regional centre under the thumb of the English Protestants, but developed industry and culture, and was at the crux of the "Troubles" leading to independence.
The city and county have a mild climate moderated by the Atlantic, so they are year-round destinations. It seldom snows or freezes hard; summers are cool, around 19°C (66°F) in July and August. The area is not particularly wet - its average annual rainfall of 732.7 mm (28.8 in) is less than London - but light showers are frequent. It's glorious when the sun shines but unless at some point in your trip you've spent 15 minutes sheltering under a shop awning on Grafton Street with cold rain dripping down your neck, wondering if it's too early to go the pub, you haven't really experienced Dublin.
Dublin Airport 📍 is 10 km north of downtown Dublin, and has excellent connections across Europe and to North America. It's within the town of Swords near the M1 / M50 junction, so it's accessible for all road routes across Ireland, and many inter-city buses run to the airport.
Dublin Port has ferries from Liverpool, Holyhead on Anglesey Wales, and the Isle of Man. Ferries from Fishguard in Wales and Cherbourg in Normandy sail to Rosslare, with train connections to Dublin. The former port at Dún Laoghaire is no longer used. For touring the north, another ferry connection is from Cairnryan near Stranraer in Scotland to Belfast then drive or bus south.
Trains from all over Ireland converge on Dublin; commuter trains make edge-of-city stops so you may not have to go into central Dublin then travel out again. Trains from Sligo, Belfast, Drogheda and the coast south to Rosslare come into Connolly Station north of the river, as do DART local trains. Trains from Waterford, Cork, Kerry, Limerick, Galway and Mayo come into Heuston 3 km west of the centre - allow 45 min if you need to change stations.
See Dublin for transport options including the Leap Card, valid for buses and DART trains across the county. Trains within this fare zone run from Dublin Connolly south along the coast to Dún Laoghaire, Greystones and Kilcoole, north along the coast to Howth, Malahide and Balbriggan, and inland to Drumcondra, Maynooth and Kilcock; and from Dublin Heuston they run west to Sallins and Naas.
Car rental: Dublin Airport has the best choice and rates. That's wrong side of the city for the south, so a city-centre rental might work better.