St Nectan's Glen is an area of woodland in Trethevy near Tintagel, North Cornwall. The site stretches for around one mile along both banks of the Trevillet River and contains a meandering footpath. The glen's most prominent feature is St Nectan's Kieve, a spectacular sixty-foot waterfall through a hole in the rocks.
The site is believed to be (and promoted as being) extremely spiritual, with many visitors leaving crystals, photographs etc, constructing piles of stones and tying ribbons to the trees.
It's a nice walk with a tea-shop at the end and the waterfall is indeed spectacular.