The old town and the harbor are very traditional. There are interesting ruins higher in the hills, and an old tomb west of the harbor.
The volunteer-run National Transport Museum is located on Howth, in the grounds of Howth Demense, although its opening hours are limited, particularly off-season when it is mainly open at weekends. Approximately 100 items of Irish transport and vehicular history are on display, including some examples of the trams which formerly ran on the Hill of Howth.
The Howth Quarry on the top of Howth Head. There are great views of Dublin bay and it is popular with walkers. Watch for procreating couples in cars though!