Most of it lies in Brazil, but the network of rivers and periodically-flooded savannah also stretches into Bolivia and Paraguay.

Unlike in the Amazon region, where tourists often complain that wildlife is difficult to see, the animals in the Pantanal look as if they are posing for photographs.

The riverbanks teem with alligators and capybaras.

Snakes can be found in almost any pool, and as the waters recede in the winter dry season, the Pantanal becomes a birdwatcher's paradise.

Most famous of all is the red-necked Tuiuiu, whose magnificent figure has become the region's symbol.

Environmental threat

The Unesco decision is likely to be welcomed on all sides.

It is now highly unlikely that the Brazilian Government will try to push ahead with plans to build a nagivable waterway through the region - an idea that had been regarded as disastrous by environmentalists.

The Pantanal also faces other environmental threats, especially from pollution and poaching, and eco-tourism itself may have had some negative effect.

But if previous experience is anything to go by, the Unesco announcement will be of tremendous benefit.

Several of Brazil's attractive colonial city centres have been restored and smartened up in recent years, thanks partly to the fact that they were declared world heritage sites.