The idea of subterranean passages linking ancient sites is a recurring motif in Irish folk memory, and while archaeology rarely confirms such stories in literal terms, they tend to cluster around sites that genuinely were significant in early medieval life. This one sits in Shanaway and is substantial enough to have earned its own name and its own mythology.

Lissymilleen is a bivallate rath, meaning it is enclosed not by one but by two concentric earthen banks with a fosse, or ditch, running between them. The interior diameter measures 38 metres, which places it comfortably within the range of a well-appointed early medieval farmstead enclosure. The inner bank is the more formidable of the two, rising to a maximum of 3.5 metres above the fosse and roughly a metre above the enclosed interior, with a steep profile that would have presented a meaningful obstacle. The outer bank is considerably lower, reaching only a metre above the surrounding ground and 1.3 metres above the fosse, which itself measures around 4 metres across. This layered arrangement of bank, ditch, and second bank was a common feature of higher-status raths in Ireland, suggesting the site once belonged to someone of local consequence. According to C. Toal's North Kerry Archaeological Survey, published in 1995, the tradition of a connecting tunnel links this fort with a smaller one situated to the north of Tarmons House. The companion fort is catalogued separately, and the two together hint at a landscape that was once more densely organised than its current rural quiet suggests.