Cow Green Reservoir Doesn't sound exciting does it. Dont judge a book by its cover.The drive there across the moors is beautiful and there a re such beautiful towns as Middleton In Teesdale to pass through or maybe stop for while but the real secret is in the outflow.The reservoir itself was built for the Tees Valley and Cleveland Water Board mainly to supply water to the industries around the Tees Estuary and Darlington but the outflow is really spectacular. The water flows out and down a water fall called Cauldron Snout a real cracker of a waterfall and is more a long cataract than a waterfall and at 200 yards (180 m) long, reckoned to be the longest waterfall in England. The falls are caused by the upper Tees passing over dolerite steps of the Whin Sill. The flow then continues down the River Tee's over a number of waterfalls until it cascades over High Force, another spectacular waterfall at 21.5 metres (71 ft.) If you ever get the chance to be in this part of the world this is a great day out.