The tallest unbroken waterfall in England is actually underground.
Fell Beck, a stream that flows down the slopes of Ingleborough in the Yorkshire Dales National Park, eventually plunges 98 metres down the main shaft of Gaping Ghyll. If you do decide to visit, please make sure you take care not to follow it by accident.
If you would like to safely explore what happens to the water as it disappears into the main chamber of Gaping Gill, plan your visit around the May or August Bank Holiday. Around the May Bank Holiday, Bradford Pothole Club set up a winch above the shaft, divert the flow of the stream and provide a thrill seekers ride into the bowels of the earth.
A similar arrangement is offered by the Craven Pothole Club around the August Bank Holiday.
The main chamber of Gaping Gill, at nearly 100 metres high, is the biggest underground cavern in the UK. A laser survey has shown that it is indeed capable of living up to the reputation it has to be big enough to contain York Minster. It might, however, be quite a squeeze getting it in down the main shaft.
There are other routes into the main chamber all of which require a reasonable level of skill, stamina and fitness. These routes should never be attempted without proper training and supervision.
The winch route, however, is suitable for anyone from 7 years upwards.
More details on citybreakinfo.com: Gaping Gill