Malham Cove, North Yorkshire.

Malham Cove is a natural limestone formation 1 km north of the village of Malham, North Yorkshire, England. A well-known beauty spot, it is a large, curved limestone cliff at the head of a valley, with a fine area of limestone pavement at the top.
On the west side of the 80 metre (260 foot) high cliff face are about 400 irregular stone steps: these form part of the route of the Pennine Way.
Originally, a large waterfall flowed over the cove as a glacier melted above it. The remnant of a stream which once fell over the cliff now flows out of the lake of Malham Tarn, on the moors 2 km north of the cove. That stream now disappears underground at the aptly named 'Water Sinks', 1.5 kilometres (one mile) before its valley reaches the top of the cove. A stream of a similar size (Malham Beck) emerges from a cave at the bottom of the cove. It used to be assumed that the two streams were one and the same. However, experiments with dyes have now shown that two separate streams go underground at different locations, cross paths without mixing behind the cliff, and re-emerge a couple of kilometres apart. This shows the complexity of the system of caves behind the cliff, which is thought to be around 50,000 years old.
The cove, along with nearby Gordale Scar, was featured in an episode of the BBC TV series "Seven Natural Wonders" as one of the natural wonders of Yorkshire. The cove was also featured in the film "Harry Potter and the Deathly Hallows (Part 1)" as one of the places Hermione and Harry travel to.
(Wikipedia).