It is also the site of England's largest hydro electric plant.
It's some 16 years since I've been to Kielder Water, and it's another of those places that's just an hours drive from Gilsland, so when a friend suggested we meet up there it was a good opportunity to check it out.
It's heavily advertised with a super website and lots of sporty things to do, fishing, sailing, mountain biking even a Kielder Marathon.
Ospreys nest there along with other birds of prey like Goshawk, but it's a huge area and chances of seeing anything has to be quite slim.
There is a Bird of Prey centre at Leaplish.
It will be great for star watching and there is an observatory.
However, it's not a great place for photographs despite all the sales pitch and after all these years it looks just what it is, a reservoir in a commercial forest so I'd guess it will be a long time before I go back.
But if you're sporty it might suit you so please read the brochure.
It's a notorious place for midges but strangely on Monday there weren't any, lots of big black flies but nothing biting.
The Osprey Ferry waiting to take people on a tour of the lake
Lots of boats
Young Pied Wagtail at the waters edge