St Ninian's Cave
Still a place of pilgrimage for Christians, St Ninian's Cave, near Whithorn, was used as the beach at the end of the May Day procession. This was where Lord Summerisle rolls the barrel of beer into the water as an offering to the God of Sea; and where Rowan first appears in the mouth of the cave, apparently ready to be sacrificed.
The cave itself is not a cave in the true sense, rather a deep cleft in the rock. The scenes where Howie and Rowan appear to enter the cave and run through it were filmed later in England.
The Beach and Cave
"And now for our more dreadful sacrifice. To those who command the fruits of the earth."