The Brusselstown Ring and Spinans Hill hillfort system sprawls across the entire hilltop, covering an enormous 32.43 hectares and making it one of the largest hillforts in all of Ireland. This isn't just a single fort but rather a sophisticated multi-layered defensive system that once commanded spectacular panoramic views across the surrounding countryside.

The complex consists of two main enclosures connected by an outer rampart that forms a roughly L-shaped boundary encompassing both hills. Brusselstown Ring itself measures about 320 metres from northwest to southeast and sits at the higher elevation, its collapsed limestone boulder walls now topped with modern field boundaries. The interior rises to several high points marked by natural limestone outcrops, the tallest reaching 1,327 feet above sea level. Meanwhile, the larger Spinans Hill fort to the northwest covers an irregularly shaped area of 550 by 320 metres, enclosed by an earthen bank that's now largely covered in peat and best preserved on the northern and eastern sides.

What makes this site particularly fascinating is the evidence of extensive settlement both within and around the fortifications. Archaeologists have identified numerous hut sites within Brusselstown Ring itself, with another twenty-three structures recorded just outside the inner walls. The outer rampart, which stretches for about 1,500 metres and includes sections of double walls with an intervening ditch, shows sophisticated defensive planning with at least three possible original entrance gaps. A stone axe discovered on Spinans Hill suggests the area was already significant during Neolithic times, though whether it was found within the actual hillfort remains unknown. Today, visitors can still trace the ancient boundaries across the grassland, though much of the complex is now overgrown with scrub and bracken.