Ludwig bought in 1967, paying something on the order of three million dollars for a block of the Jari valley usually given as four million acres - a holding larger than the state of Connecticut, straddling what is now the Pará-Amapá border. Published figures for the size vary, which tells you something about how carefully the transaction was examined at the time. His theory was straightforward and, on paper, brilliant. Mixed rainforest yields commercial timber only sparsely, so clear it and replace it with dense plantations of Gmelina arborea, a fast-growing Asian hardwood. Feed the gmelina to a pulp mill. Ship the pulp out through a deep-water port on the Jari. Ludwig owned tankers, so the shipping was the part he understood best of all. He was seventy years old when he began.

The workforce needed somewhere to live, so Ludwig built them a town. Monte Dourado - Golden Mountain - went up from 1967 on the Pará bank of the Jari as a planned company settlement: streets laid out in advance, around three thousand houses, schools, a hospital, roads, an airport and a port. He asked the Brazilian government to help pay for the civic half of it. The government refused, and that refusal became one thread in a long, souring relationship between the Brazilian state and a foreign billionaire quietly assembling a private domain in the Amazon at the very moment the military government was pushing its own development schemes into the same forest. Seventeen kilometres away, Munguba became the industrial half of the operation - the port, the power plant, the mill - tied to Monte Dourado and the plantations by some seventy-five kilometres of railway.

The forest declined to cooperate. Gmelina, magnificent on good ground, grew poorly on the sandy and lateritic soils of the Jari, and by 1981 it was being replaced with pine and eucalyptus - a rewrite of the central premise a decade into the project. An attempt at irrigated rice on the floodplain swallowed enormous quantities of lime and fertiliser and never paid for itself. Cattle did better. Kaolin, the white clay used to coat paper, turned out to be genuinely valuable and is still mined in the Jari valley today. But by the end the arithmetic was hopeless: hundreds of millions of dollars sunk, a mill running below capacity, and a founder in his eighties. Ludwig gave up in May 1981. The following year he handed the whole project to a consortium of Brazilian businessmen and took no payment for it. What changed hands was the debt.

Monte Dourado did not disappear. In 1983 it became a district of the municipality of Almeirim, and the mill at Munguba went on making pulp under a succession of Brazilian owners. Ludwig died in 1992, aged ninety-five. Across the water, meanwhile, a very different settlement had grown up on the Amapá bank: Beiradão - the big riverbank - where people the company town could not or would not house built their own place on stilts above the river. In 1987 Beiradão became the municipality of Laranjal do Jari, and it is now substantially larger than the planned town that called it into existence. A ferry runs between the two. Monte Dourado is otherwise reached by the PA-473 road from Almeirim, or by air. It remains exactly what it was drawn to be: a tidy grid in the forest, built for a project that never worked.