The need was simple and inarguable: the East Midlands was growing, and Peterborough, in particular, was thirsty. Engineers picked the Gwash valley because the clay subsoil made for a watertight basin, because the topography allowed a relatively short dam, and because the catchment could be augmented by pumping. Most of the water in Rutland Water did not fall on Rutland. It is lifted from the River Welland near Tinwell and from the River Nene upstream of Peterborough, then released downstream when towns need it. The clay dam at Empingham is 115 feet high and roughly 1,300 yards long, with its base 890 yards wide. The clay came from pits dug inside the future reservoir bed, a tidy piece of engineering that left nothing visible. From the air the dam reads as a low landscaped hill, not a wall.

Nether Hambleton and most of Middle Hambleton were demolished before the flooding. Upper Hambleton survived because it stood on the ridge between the Gwash valley and its side valley, and that ridge is now the Hambleton Peninsula, a long finger of pasture and woodland projecting almost across the lake. Normanton's church, St Matthew's, was the iconic save: the lower walls were reinforced and packed to resist water damage, the floor was raised, and the upper structure now sits like a small lighthouse at the shore, telling visitors the story of the reservoir's construction. Some funerary monuments were carried to Edenham in Lincolnshire and rest there now, in a churchyard that was never meant to receive them.

In 1996 the Rutland Osprey Project began to release young ospreys onto the reservoir, the first successful reintroduction of breeding ospreys to central England in 150 years. One of the early birds, ringed and tracked obsessively, became locally famous as Mr Rutland. By 2021 there were 26 ospreys living in and around Rutland Water, fishing the same shallows where coarse fish pumped in from the Welland and the Nene now thrive: roach, bream, pike, zander, wels catfish, carp. Other birds matter too. Roughly four percent of Europe's wintering gadwall population spends the cold months on the western lake, alongside shoveler, lapwing, goldeneye, tufted duck, pochard, great crested grebe. The western 1,333 hectares carry international wetland protection under the Ramsar Convention. Until 2019 the Anglian Water Birdwatching Centre hosted the British Birdwatching Fair every August, an event that brought tens of thousands of people each year to a place that, a generation earlier, had been farmland.

In early 2021, the reserve manager Joe Davis was overseeing the routine draining of a lagoon when he saw a vertebra in the mud. What lay below turned out to be a Temnodontosaurus, an ichthyosaur about ten metres long, with a skull block weighing close to a tonne. It is the largest and most complete fossil of its kind ever found in the United Kingdom, a 180 million year old sea predator pulled from the floor of an artificial twentieth-century lake. The valley that became Rutland Water had been a tropical sea before it was farmland, and the reservoir simply happened to expose what was always there. It is hard to think of a tidier piece of geological irony.

The 23-mile perimeter track is one of the most popular cycling and walking circuits in the Midlands. The Rutland Belle pleasure cruiser carries visitors between the Egleton end and Whitwell. Sailing boats lean across the water on summer afternoons, and the Rutland Sailing Club runs a serious dinghy programme that has produced Olympic squad members. At Sykes Lane there is a visitor centre with mini golf and Rutland souvenirs, which is the sort of detail that tells you the reservoir has been folded entirely into ordinary life. The villages are gone. The lake is loved. Both of those facts are true at the same time.