Complex sentence: Ordnance Survey mapping It is located on the east side of the island and there is a quay, at the southern end of which is the Blockhouse, a 16th-century fort built to defend the harbour from attack.
Split into simpler sentences: Ordnance Survey mapping It is located on the east side of the island and there is a quay. At the southern end of the harbour bay is the Blockhouse, a 16th-century fort built to defend the harbour from attack.