A Martello Tower is a small defensive tower. These are fairly common in the UK and Ireland, as well as other countries in the British Empire. One can be found in Seapoint, which is a small stretch of seafront in Dublin which has a preserved tower.
The tower itself is interesting to look at and forms part of the history of Dublin. It is in good order, and now houses the headquarters of the Genealogical Society of Ireland. Set between Blackrock and Monkstown, it is in a lovely as well as useful location which has a beach and bathing area.
Address: 2-16 Brighton Vale, Dublin, Ireland