The North Pier is a classic example of Scottish vernacular harbour work. It comprises a pier of rubble construction, with a substantial bulwark on its seaward face, to protect the wide quay from over-topping seas in heavy weather. The course of the pier is somewhat crooked, reflecting the strategy of the builders to construct it from strong point to strong point along the natural rock skerry which forms its foundation. The dry-stone, rubble construction of this pier gives it great character and the surfaces reveal many examples of repairs to the pier, using a variety of different strategies for placing the stones. The outer, seaward face of this pier contains in places re-used stone with rolled moulded margins, presumably coming from the ruined castle or cathedral in the 18th and 19th centuries.

The North pier has a number of important features along is length, including cyclopean stone mooring pawls, stone stairs leading to the bulwark and a stone slipway in the harbour where the pier joins the Shorehead quay. There is also a stone-built ramp at the root of the pier leading down onto the shore. This ramp is of indeterminate age but it connects with a rock-cut roadway leading towards the castle, where there was an important landing beach. The outer, seaward end of the North pier is of 19th and 20th century date, reflecting efforts to improve the access to the harbour in heavy weather. It is of typical Victorian and later cement construction, much more rectilinear than the earlier work at the shore-ward end. This later extension is fitted with cast-iron mooring pawls.