This week’s dream: the wetlands of Argentina

The Esteros del Ibera are the least known of Argentina's natural wonders, says Philip Smith in the Guardian. A world away from "the pampas and gaucho land of the popular imagination", these wetlands in the north of the country are nonetheless vast, their 63 lagoons stretching across an area the size of Wales, and home to an astonishingly rich ecosystem. They became a nature reserve in 1983, when hunting was banned and the indigenous Guarani people retrained as guides (the region's name derives from the Guarani for "bright water", y bera). More recently, they've opened fully to tourism, with a flurry of low-rise, eco-friendly developments.

The town of Colonia Carlos Pellegrini, an overnight coach journey from Buenos Aires, is "an ideal base for exploring the Esteros", though little more than "a few sandy crossroads" itself.

In recent years, a number of lodges have opened around here – among which only the Posada de la Laguna enjoys a position on the waterside. Its four acres of gardens appear to dissolve gradually into the lagoon, so dense are the hyacinths and lilies at the water's edge. Leaving here by boat, you have to navigate a maze of embalsados - islands formed from knots of vegetation, some so big they can support trees. Blown by the wind, they make the Esteros "an ever-changing delight".

The lagoon system is so vast, you'll rarely come across other humans. However, yacares - a local species of alligator - soon become a familiar sight (some people will tell you they're so fat and happy feasting on fish, it's safe to swim with them). Otherwise, each new site you visit offers its own "uncanny array of river otters, bizarre spiders, capybaras (which are like guinea pigs on steroids), snakes, butterflies and howler monkeys" - as well as spectacular birdlife, including eagles, ibises and hummingbirds.

The airline Iberia (0870 609 0500) flies Heathrow to Buenos Aires from £674 return. Posada de la Laguna (+54 11 4797 7449) has doubles for $170pp per night. ·