The northern half of this 18-metre-high tower still reaches skyward, a remnant of what was once a formidable stronghold of the Earls of Desmond. The tower originally measured about 10.5 by 9 metres, with walls 1.8 metres thick, and contained five storeys; the bottom two levels were vaulted for added strength. Though the south wall and about half of the sides have collapsed, what remains gives a clear sense of the castle's former imposing presence.

The castle complex included more than just the main tower. A substantial bawn, or fortified courtyard, measuring roughly 55 metres square, surrounded the castle with walls that reached 9 metres in height and were 1.7 metres thick. Today, parts of this defensive wall have been incorporated into farm buildings, but traces of the original fortification remain visible. A particularly intriguing feature is a round turret containing a spiral staircase that once led to a sallyport, a concealed exit near a pool that would have allowed defenders to launch surprise attacks or escape if necessary.

The castle's turbulent history came to a head during the Cromwellian conquest of Ireland, when Sir Henry Waller captured it for Oliver Cromwell in 1650. Archaeological investigations in 2005 found no evidence of earlier settlement in the immediate vicinity, suggesting the castle was built on previously undeveloped land. First documented by Westropp in the early 1900s, Shanpallas Castle continues to intrigue historians and visitors alike as a tangible link to Ireland's medieval past and the powerful Desmond dynasty that once controlled much of Munster.