Serra da Barriga belongs to the southern Borborema Plateau, a band of uplands that catches the wet air coming off the Atlantic and holds it. The serra runs roughly 8.6 kilometres end to end and reaches about 3.35 kilometres at its widest, covering something near 28 square kilometres of high ground. The Açucena creek rises on it and drains north into the Mundaú valley, which means the summit had what a besieged town needs most and can least easily fake: its own water. Add deep soil for cassava and maize, timber on the slopes, and sightlines in every direction, and the choice stops looking like luck. At the time, none of this was Alagoas. The captaincy was Pernambuco, and the sugar plantations that ringed the serra were the reason anyone was running for it.

The settlement on the ridge was called Cerca do Macaco, also recorded as Cerca Real dos Macacos - the walled place, the royal enclosure. It was the seat of what the Portuguese rendered as Angola Janga, Little Angola, and after 1654 it is thought to have held as many as ten thousand people. A Portuguese account of one Palmares settlement in 1645 counted 220 buildings, a church, four forges and a council house, which tells you these were towns rather than camps: places with blacksmiths, planted fields, government and a place to argue in. The defences were made of what the hill offered - fences, walls, and traps set into the approaches. Zumbi, who became commander of Palmares' forces in 1675 and later its king, is said to have been born on this serra in 1655.

Terrain that protects you can also trap you. In January 1694 the bandeirante Domingos Jorge Velho brought a force reported at some six thousand men against the serra, well provisioned and - crucially, for a hill defence - carrying artillery. The advantage the slope had given Macaco for decades evaporated the moment the attackers could stand off and shoot up at the walls. The siege ran forty-two days before Cerca do Macaco fell on 6 February 1694. The accounts that survive describe two hundred of its people dying by their own hand rather than be taken back into slavery, which is the clearest surviving statement anyone left about what this ground had been worth to them. Zumbi escaped down the far side and kept resisting for nearly two more years; he was killed on 20 November 1695.

For most of the following three centuries the serra was farmland, and the town it had held existed mainly as a name. That changed in the twentieth century, slowly, then officially: IPHAN, Brazil's national heritage institute, listed Serra da Barriga in 1986, and the site has since been recognised as Cultural Heritage of Mercosur. Archaeological work on the hill has complicated the story in a useful way. The material coming out of the ground points to substantial Indigenous presence alongside African, which fits a reading of Palmares as a refuge for more than one kind of person fleeing the plantation economy. The serra is not a ruin you can walk through. What it holds is stratigraphy, sightlines, and the fact of the place itself.

The Parque Memorial Quilombo dos Palmares opened on the summit in 2007. It is not a reconstruction in the archaeological sense - it is a memorial, with dwellings and ocas built in period style, structures for processing cassava, viewpoints over the plain, and audio narration offered in four languages. Brazil describes it as the country's only thematic park dedicated to Black culture, and visitor numbers have been climbing. Every 20 November, Brazil's Day of Black Consciousness and the anniversary of Zumbi's death, people come up the hill in numbers - schoolchildren, quilombola delegations, capoeira groups, families. Calling it tourism undersells it. For a great many Brazilians the climb up Serra da Barriga is closer to pilgrimage: a walk up to the one piece of ground where freedom was not granted but taken and held for most of a century.