Mither Tap Hillfort was built upon one of the four summits of Bennachie. Possibly occupied as early as 1000 BC, it was over 500 metres above sea level and would have doubtless have been a fairly bleak residence for most of the year. The defences, which doubtless evolved over time, consisted of inner and outer stone ramparts. Both were over 7 metres thick with evidence of a parapet walkway at least on the lower/outer wall. The entrance consisted of a hornwork - an Iron Age version of the medieval barbican. A number of roundhouses seemingly existed between the inner and outer ramparts and a square structure, perhaps some form of hall, was built in the centre.
The only reliable dating of the structure comes from analysis of charcoal remains which were dated to AD 340-540 and AD 640-780 respectively. It is uncertain therefore whether the fort existed at the time of the Battle of Mons Graupius (AD 83).