With many such structures dotted around Northern Ireland, they are certainly well worth a visit, with their stunning windows onto the past.
Here are some suggestions for a memorable day out.
5. Kinbane Castle
On a white limestone headland outside Ballycastle, these ruins of an outer wall and keep are a truly impressive sight. Originally constructed by the MacDonnells in the 16th century, the castle was rebuilt following English sieges in the 1550s. In Victorian times, it became known as Reubens Castle - guides from the Giant’s Causeway would row to the castle to collect the mineral spar (natrolite) to sell to tourists. Today, the castle has been classified as a State Care Historic Movement. For more information, go to discovernorthernireland.com/things-to-do/kinbane-castle-p706881 Photo: DiscoverNI
6. Shane’s Castle
On the coast of Lough Neagh at Antrim, this imposing bastion has been the home of the O’Neill family - the kings of Ulster for a millennium - since 1345. Originally known as Edenduffcarrick Castle, it earned its current name in 1722 in honour of Shan McBrien O’Neill. Unfortunately, the castle was burnt down in 1816, with its ruins being left behind. Nonetheless, the O’Neill family still resides on the grounds, in a house built in 1958. Keep a look out for a sad-looking female face on one of the eastern walls - according to legend, if she falls, so too will the O’Neills. Tours by appointment only during the summer. For more information, go to visitantrimandnewtownabbey.com/things-to-do/heritage-attractions/shane-s-castle/ Photo: Visit Antrim and Newtownabbey
7. Kilwaughter Castle
Originally constructed as a four-storey tower with bartizan turrets in 1622, this building near Larne had its defence systems removed and transformed into an English-style mansion in 1806 by none other than John Nash, designer of Regent Street. Throughout the rest of the 19th century, further alterations were made, including the installation of a glass-roofed library and an octagonal tower. In 1982, the property was bought by the Ferguson family who intended to save the Grade B listed building. Only open on Open Days. For more information, go to kilwaughtercastle.com/ Photo: Kilwaughter Castle website
8. Dundrum Castle
Not to be confused with the castle in County Dublin, this castle was built as part of a coastal defence system by John De Courcy, the Norman knight who built Carrickfergus Castle. On a wooded hill near Newcastle, the castle was meant to control land routes from Downpatrick to Drogheda. King John seized control of the castle in 1210 and incorporated the distinctive gatehouse and keep that you can see today. For more information, go to discovernorthernireland.com/things-to-do/dundrum-castle-p675301 Photo: DiscoverNI