Tennyson made this place famous in his "Idylls of the King" when he described waves bringing the infant Arthur to the shore, where he was plucked out by Merlin and carried to safety. Local legend has long associated this cave - which fills with water at every high tide - with the great enchanter. It is certainly a place of considerable atmosphere, where one might indeed expect to see Merlin approaching, with his staff held up to illuminate the darkness of the cave.
Until recently there were well-defined steps leading down to the cave. Those have washed away and are now blocked off. The only way down today is by a rough trail over the rocks down to the beach. This path doesn't appear to have been developed by the staff at Tintagel; rather it seems that people simply found another way to reach the cave when the stairs became an inviable option.
The cave fills with water at high tide, but the sandy floor absorbs most of the water to make the cave explorable at low tide. The cave goes all the way through the rock, and there is a smaller tributary cave that can be entered on the southern side. It was pitch black, but we were curious and walked all the way back until we found the wet back wall.
To see a Streetmap.co.uk map of the area around Merlin's Cave at Tintagel, click here.