Goat, or Dalkey Castle, has an overall form of a single cuboid-shaped keep structure, typical of the ‘Irish’ castle. The materials used to build the castle are somewhat difficult to fathom. Granite has been quarried in Dalkey for many years, however the exterior of the building had no visible crystals, but this could be due to extreme weathering or a buildup of dirt. The stone is a pale grey colour, lending itself to limestone, and built in a rubble-wall fashion. The mottled colour of the stones further matches the characteristics of limestone, as granite doesn’t form as distinctly with its surrounding mineral deposits as limestone does. It is worth mentioning that Archibald Castle, situated almost directly opposite Goat Castle, is made from granite, although looking at it it was almost as difficult to tell. The stone around the main door and windows is carved into shape. It is a much lighter colour, probably from its finish, and the fact it was carved suggests it is probably limestone, a much more malleable material. The heavy refurbishment of the castle means that it could also have been a much more recent addition, meaning a potentially different stone, as the windows to the rear of the castle have no such luxurious framework, although the windows at the back are much smaller and would not need to make such an impression. The castle has numerous distinctive features. It has a large number of arrow slits, which is not uncommon, however they are not limited to just the upper floor and battlements; the ground floor has several similar openings, especially to the rear of the building. The parapet of the battlements seems unusually high, but is built in the usual crenellated style, with variations in height. There is a marked lack of opening on the ground floor, save for the large arched front door and a few very small windows, which are scattered seemingly randomly across the facade and other walls; this was probably for defensive reasons. The upper floor has several larger windows, possibly opening into more luxurious or important rooms. The sturdiness of the building along with its lack of adornment suggests that Goat Castle was used purely in a defensive capacity, which makes sense considering it is situated in a vulnerable region, beyond the help of Dublin but very near the shore. It is likely that it had a permanent garrison because of this, so it would also have a residential function. The extra arrow slits and higher parapet suggest a need for extra defence. It is possible that Goat Castle was the home of a very prominent dignitary or other similar person. Another possibility is that it was used to store expensive trading goods that came in by sea, requiring the extra protection. Whatever the function of the building, it is spectacular to look at, its survival a testament to simple but effective architecture.