We are walking around the castle towards its Barbican and Gatehouse.
The inner Keep and a round tower augmented with buttresses or spurs..
As you can see the gatehouse is high in the wall and approached by an elevated path leading from an outer Barbican.
Above the Gatehouse. Note the two 'murder holes' from which from which all manner of things could be dropped on attackers. At the back of the two apertures are the slits through which the portcullis was raised and dropped.