The site’s history stretches back to the late 12th century when King John granted the Manor of Knockgraffon to Philip of Worcester, with Tullamain existing as a sub-manor within this larger estate. By the early 14th century, the fortification had passed into the hands of the Comyns family, as recorded in administrative accounts from 1308-9 that reference their presence at “the manor of Tullamelan”.

The main motte stands as a formidable earthwork, reaching over 5 metres in height with a roughly circular shape that has been somewhat altered by fallen trees and natural slippage over the centuries. Its flat top, measuring approximately 16 metres north to south and 12.8 metres east to west, shows evidence of various depressions, likely caused by uprooted trees and erosion. The defensive capabilities of the site become clear when examining its complex system of fosses (defensive ditches) and banks; the primary U-shaped fosse reaches depths of nearly 3 metres and is surrounded by substantial earthen banks that would have made any assault extremely challenging. The northwestern side of the motte appears particularly steep, though centuries of erosion have partially filled the protective ditch on this side.

What makes Tullamain particularly fascinating is its elaborate bailey system, which extends in multiple directions from the central motte. To the southwest lies the primary bailey, a defended area measuring roughly 28 by 63 metres, enclosed by banks rising to 3.65 metres and accompanied by an outer fosse. A possible second bailey exists to the northwest, though less heavily defended, spanning approximately 52.5 by 26 metres. South-southeast of the main motte, archaeologists have identified a large secondary mound, 28 metres in diameter, which likely formed part of the entrance defences alongside a rectangular area defined by substantial earthen banks. Local tradition holds that numerous springs exist throughout the site, which would have provided the essential water supply for the castle’s medieval inhabitants.