The house tower with its outer wall and corner towers, of which the remains of two are still there, was built in the 15th century. Many of these "tower houses" were built in Ireland during this period. The one at Ross Castle was restored as authentically as possible by the Irish state with great attention to detail and is therefore considered a special feature.
Inside there is old furniture from other places, but it could have been there too. You can only visit the inside of the tower with a guided tour and photos are not allowed. I cannot understand the reasons for this, but the owner of the house decides. Taking part in a guided tour is highly recommended. Among other things, you learn why the spiral staircases run clockwise and what this has to do with the demonization of left-handed people, which lasted well into the 20th century.
From the outside you can see the renovations in the 17th and especially the 18th century, when the castle was converted into a barracks.
After the victory over Napoleon, this barracks also lost importance, as a French invasion was no longer the biggest concern. The property was returned to the owner family. They had naturally made their homes comfortable elsewhere in the meantime, and a medieval dwelling is anything but comfortable.
In the 19th century, the castle was romanticized in keeping with the spirit of the times, without considering the history of the buildings.
A British-Irish peculiarity is the roof tax. The owner had the roof removed for this reason. Otherwise he would have had to pay taxes for an unused second home. The renovations and the missing roof caused the tower in particular to fall into disrepair.
Until people remembered the cultural heritage and restored it.