Kolindsund is a glacial trench, twenty-five kilometres long, hemmed by slopes rising as much as thirty-five metres above the flat. In the Stone Age it was not a valley at all but a saltwater sound, open at the Grenaa end and cutting clean through the landscape — which meant that north-eastern Djursland was an island. The sea closed the door slowly. Wind-driven sand piled up near Grenaa while sea levels shifted and the land itself rose, released from the weight of the ice. By the Middle Ages the sound had become a shallow freshwater lake, navigable but only a few metres deep and thick with reeds. On its bottom, silt and clay settled together with peat into gyttja, the dark organic mud that would later make the drained bed such extraordinary ground to farm.

In March 1872 a joint-stock company was formed in Copenhagen with a single purpose: to remove a lake. Work began that May. Over the next two years, crews cut a canal along the northern edge of the sound and another along the southern edge, intercepting the streams that had always fed it, then drove a third channel straight down the middle of the old lakebed to bring water to the pumps. There were no machines for this. The canals were dug by hand — pick, shovel, wheelbarrow — through kilometres of waterlogged clay, in a country that had not yet seen a motor car. Two pumping stations went up, powered by steam engines with windmills to help them, an arrangement that lasted into the 1930s before electricity took over.

The pumps started on 3 May 1874, and the water began to fall at about 1.3 centimetres a day. It is a tiny number and an enormous one. Through that summer the lake retreated towards its deepest channels and then stopped being a lake, leaving roughly 2,800 hectares of black, wet, absurdly fertile ground. By 1877 most of it had been sown to grass. From 1880 the company built farms across the new land and appointed managers to run them; in 1921 the holdings were sold off to private owners. The sund now grows wheat at more than 100 hkg per hectare — over ten tonnes — alongside rapeseed and other cereals, with smaller plantings of spinach, beets, poppy and caraway.

The original calculations assumed the pumps would only have to lift the rain that fell on the sund. Reality asked for roughly twice that. Groundwater from the surrounding hills does not politely stop at a canal; it travels underneath and resurfaces inside the basin, and Djursland's limestone adds karst channels that behave like hidden plumbing. At the Enslev station, close to half the water being pumped out has been calculated to find its way straight back in below ground. Three stations — Fannerup, Enslev and Alleslev — now share the work, lifting water some five metres into the canals that carry it to the Kattegat at Grenaa. The Fannerup station, built in the 1930s, is the most visible monument the enterprise has: a modest brick building on which every field around it depends.

Since 1999 an association called Kolindsunds Venner — the Friends of Kolindsund — has argued that the sensible thing to do is stop. Re-flood the basin and Denmark gets back something it deleted: a lake that would be the largest in Jutland by area and the second largest in the country after Arresø, with the wetland, the birds and the recreation that follow. Against that stand 2,800 hectares of some of the best soil in Denmark, worked by families for generations and kept dry by levies those families pay. Norddjurs and Syddjurs municipalities have committed to drawing up an idea catalogue for the area's future. A century and a half after the pumps first turned, the question of whether Kolindsund should be a field or a lake is genuinely undecided — which is a strange and rather hopeful thing to say about a landscape that looks so settled.