Iguazu Falls: 2-3 May

I shuffled towards the edge, one small tentative step forwards at a time. The thunder of water filled my ears, drowning out all other sounds. Jets of spray shot up from below drenching my sholder and then my leg. I gripped the railing and peered over the side at the mighty torrent of treacle-brown water. This was it - the Devil's Throat (Garganta del Diablo), the biggest and most powerful of cascades in the Iguazu falls.

I'd arrived overnight on an 18-hour bus ride from Buenos Aires. As I trundled northwards, I left behind the guachos and their cattle grazing in the long green grasses of the pampas. By morning, the muted greens of the south had been replaced by the deep red earth and verdant forests of the tropics.

The Iguazu falls are a freak of nature, a geological oddity. The Rio Iguazu is a broad but unremarkable brown river that meanders for several hundred miles from north to south forming a natural border between Brazil and Praguay. Then suddenly, just before it joins the much mightier Rio Parana, it passes over the edge of a basalt plateau and plunges some 80 metres over a series of natural cliffs. The result is truly breathtaking - millions of cubic metres of water flow into vacant space creating some magnificant cataracts.

To appreciate the sheer scale and magnificance of the falls you have to visit them from both banks of the river. I began in Argentina taking the "up close and personal" tour. I wandered along footpaths precariously suspended amongst the falls: one moment I was perched above the lip of a thundering cascade, the next minute I was getting soaked in the spray at the foot of a huge deluge of water.

The atmosphere was close and humid, near perfect conditions for butterflies. I marvelled at the diversity of species: iredescent blue divas, some with fire-red wing tips, small fluttering yellow emperors, magic looking silver streaked ones. But my favourite species I named "target 88"; its wings had concentric black and white circles with a perfect 88 in the middle framed in bright red.

Day two took me to the Brazilian side of the falls - a 30 minute hop across the frontier passed languid border guards and uninterested immigration officials - for the "panoramic" view of the falls. Set back across the river you can absorb Iguazu's full drama, the pouring water, frothing rock pools, spray making the verdant jungle sparkle amidst rainbows.

Seeing such an awesome display of nature, like a volcanic erruption or a tsunami, reminds you of how small an insignificant we are, how quickly we can be wiped out, and how, ultimately, planet earth will always outlive us. I left Iguazu in awe for another bit of South American wilderness that had also received rave reviews: the Pantanal.