File:Trim Castle November 2013.jpg
The surviving curtain walls are predominantly of three phases. The west and north sides of the enciente are defended by rectangular towers (including the Trim Gate) dating to the 1170s, the Dublin gate was erected in the 1190s or early part of the 13th century and the remaining wall to the south with its round towers dates to the first two decades of the 13th century. There are two main gates into the castle. The one in the west side dates to the 1170s and sits on top of s a demolished wooden gateway. The upper stories of the stone tower were altered to a semi-octagonal shape, c. 1200. A single round towered gate with an external barbican tower lies in the south wall and is known as the Dublin Gate. It dates from the 1190s or early 13th century and was the first of its type to be constructed in Ireland.
Apart from the keep, the main extant structures consist of the following: an early 14th century three towered fore work defending the keep entrance and including stables within it and which was accessed by a stone causeway crossing the partly filled-in ditch of the earlier ringwork; a huge late 13th-century three aisled great hall with an under croft beneath its east end opening via a water gate to the river; a stout defensive tower turned into a solar in the late 13th century at the northern angle of the castle; a smaller aisled hall added to the east end of the great hall in the 14th or 15th century; a building (possibly the mint) added to the east end of the latter hall; two 15th- or 16th-century stone buildings added inside the town gatehouse, 17th-century buildings added to the end of the hall range and to the north side of the keep and a series of lime kilns, one dating from the late 12th century the remainder from the 18th and 19th centuries.