Dalkey is a small, upscale village on the coast south of Dublin, reachable in half an hour on the DART train from Pearse Station. It makes one of the best day trips from the city — scenic, walkable, and blissfully far from Temple Bar.
The centre of the village is compact and pleasant, with good restaurants alongside the usual pubs. A walking tour takes you past several medieval castles: Dalkey Castle (also known as Goat's Castle) and Archbold's Castle both date from the fifteenth century. Follow the winding streets eastward and you reach the coast, where Dalkey Island sits just offshore — its ruins of a Napoleonic-era battery and an early medieval church visible from the mainland.
Sorrento Park, nearly hidden on a steep little hill, offers views along the coastline and out to the island, and on a clear day you can see all the way to Wales. For a longer walk, the Vico Road south toward Killiney has some of the best coastal scenery in the Dublin area, and the climb up Killiney Hill or the old Dalkey Quarry caps the visit.