Dublin's most important medieval port has long since settled into its role as an elegant dormitory village, but there are some revealing vestiges of its illustrious past, most notably the remains of three of the eight castles that once lorded over the area. Dalkey is small enough that you can get around on foot.
Malahide (Mullach Íde) was once a small village with its own harbour, a long way from the urban jungle of Dublin. The only thing protecting it from the northwards expansion of Dublin's suburbs is Malahide Demesne, 101 well-tended hectares of parkland dominated by a castle once owned by the powerful Talbot family.
Sandycove has a pretty little beach and a Martello tower – built by British forces as a lookout for signs of a Napoleonic invasion – now home to the James Joyce Museum. There are really only two things to do here: visit the Martello Tower and, if you're brave enough, get into the water at the adjacent Forty Foot Pool.