Q sets Ia in an area centred on St Ives Bay, Hayle Towans and the north-eastern part of the Penwith moors.
Gulland Point and Lighthouse in the novel are based on Godrevy Point and Lighthouse (SW580433).
Revyer hamlet and towans take their names from Riviere hamlet and towans at Hayle (SW560380) but are relocated to the west of the River Hayle and sited at the place where St Uny's church now stands (SW548378).
Round House Chapel at Revyer is based on the Round House Chapel at Copperhouse, Hayle (SW570380), constructed c.1785 and at which John Wesley preached in 1787; demolished c.1820. It is relocated in the novel to where St Uny's church now stands (SW548378).
Ardevora is based on St Ives; and the Island at Ardevora upon the island at St Ives.
Towans from Gulland Point to Ardevora are based on the Towans which stretch from Godrevy to the River Hayle, plus the present day golf links at Lelant.
The bar at Revyer is based on the bar to the River Hayle.
Noon Water in the heart of the moor is based upon the stream running south from Amalwhiddden (SW488372) and Amalveor (SW487378) in the parish of Towednack.
The Roman hill fort lying between Noon Water and Revyer is based on the Iron Age fort on Trencrom Hill (SW518363).
Zennor stone, the Logan and the Witch's Crown are based on the logan stone and quoit at Zennor (SW460380) and the quoit at Mulfra Hill (SW454354).