The southern curtain wall has two towers; the Carrickfergus tower to the west and the Montagu tower to the east. The curtain wall and the main gatehouse were probably built at the turn of the thirteenth century. Access to the gatehouse is across the ditch which originally would have been protected by a drawbridge. The central passage of the gatehouse posed a particular problem for any attacker as it not only has a gate and a portcullis but also has guard rooms on each side with arrow slits. Another gate at the far end of the passage added yet another obstacle to be overcome.
Once through the gatehouse you enter the bailey. The bailey is split into two wards by the foundations of a half-finished church. The outer ward is the larger of the two wards and around its edge are the remains of several buildings that would have stood against the curtain walls. In the south west corner of the outer ward are the remains of a chapel and domestic buildings. The main hall would have stood against the west curtain wall along with the kitchen. The only surviving parts of this range of buildings are a section of the hall and a tower known as the Lion Tower. On the tower is a carving of the Percy family lion which gives the tower its name.