Polruan is part of the parish of Lanteglos-by-Fowey which is bounded by water on three sides - Penpoll Creek to the north, the Fowey River to the west and the sea to the south.

The ruin of St Saviour's church on the hill above Polruan dates to the 8th century. It was a landmark for shipping, and also, in times of war, a vantage point for observing the approach of enemy shipping to the strategically important Fowey harbour.

Polruan also has a blockhouse fortification that guards the entrance to the river Fowey, one of a pair - its partner being situated on the Fowey side of the river. Between the two blockhouses was strung a chain to prevent enemy ships entering the harbour, the chain being lowered for friendly vessels. This was primarily used during the wars with the Dutch.