'Where am I?' I asked in my best Mandarin. Obviously, my best wasn't good enough. The shop assistant gazed momentarily in disbelief across her bowl of noodles at me, then spluttered out half a mouthful as she erupted into a fit of hysterical laughter.

The bright yellow, orange and red mineral deposits, which formed around a set of geysers about 100 kilometres west of the capital, appeared to be the surreal vision of an inspired sculptor. I had never seen anything like it before, and the fact that I could find no reference to the geysers in the guide books only served to increase my interest. I made a copy of the page giving directions and started plotting the trip.

It might sound like the latest dance craze, but in fact 'doing the loop' refers to Thailand's most exciting journey - a 600-km circuitous route from Chiang Mai to Mae Hong Son and back. It climbs and dips, swerves and curves round more than 3000 bends as it passes towering mountains, tranquil valleys, market towns and hilltribe villages on the way.

We now know there are no pterodactyls, but in every other sense the 'lost world' of Conan Doyle's fantasy novel 'The Lost World' exists, in the southwest region of Venezuela, near the borders with Brazil and Guyana. It is called the 'Gran Sabana', and though scientific expeditions have removed some of its mystery, more than half of the hundred or so table mountains, or 'tepuis' as they are known, have still not been explored.