The valley was steep-walled and clad with green forest and arching bamboo. New plant species were appearing; pink and red flowering begonias, giant horsetails, palms, ferns and different glossy green and thick-leaved shrubs. As before, Felix told us the quechua names of many plants and explained their uses; treatment for fever, hangover cure, seasoning for cooking, dyes etc. We sampled fruits and nibbled nuts as we descended, crossing several fast-flowing sidestreams by stepping stones or rustic log bridges. Our bodies enjoyed breathing the humid, oxygen-rich air of these lower altitudes.

Reaching a grassy opening, we stopped to rest and buy some granadillos at a small trackside stall (the first of several as we entered the more populated and more cultivated lower part of the valley). We were enjoying the more relaxed walking, with a cooling breeze blowing up the valley as we sucked the sweet juice of the granadillos and admired the new flowers and orchids that lined the track.

Soon we were passing through small coffee and banana plantations, and adobe huts appeared frequently alongside the widening track, which eventually led us into the small town of La Playa. The electricity wires and television blaring through open doorways told us that we were back in "civilisation". The far end of town was a gathering point for trekkers - we stopped for a cold drink and hot lunch at an outdoor restaurant, listening to the sounds of Bob Marley and other trekkers chatting and sipping beers. We were definitely back in civilisation, but didn't feel quite ready for it yet.

From here we started walking again, taking a short 2km stroll along the broad stony bed of the Vilcabamba River, crossing the Salkantay on a long suspension bridge just before it merged with the Vilcabamba and pushing on into the narrowing gorge of the river. We stopped at a secluded flat spot, where Felix pointed out the side path to the "secret" hot spring, a small pool of clear, warm water set amongst the rocks.

We had a latish start this morning - the sun was already heating the floor of the valley when we set off at 9am to wander along the stony river flats, past carex rushes, pink-flowering orchids and the odd balsa tree (so now I know where the model planes I made as a kid came from). The pink seed heads of Colombian feather grass covered the steep valley slopes - like many introduced plants, beautiful but dangerous! Leaving the flats, we crossed the river on a solid metal girder bridge, built to replace one swept away in disastrous floods 10 years earlier.

The gorge narrowed and steepened after the bridge and we headed gently up a wide dirt road, passing small banana plantations that clung to the steep slopes. A little later we crossed the outlet of the hydro-electric station higher upstream, the water jetting out fiercely from the rock face like a giant fire hydrant. Coffee, banana and fruit plantations were now becoming more common. Then, rounding a bend, we saw it for the first time rising sheerly and sharply above the Vilcabamba River; the site of Machu Picchu.

Spurred on by the sight, we crossed the river, now known as the Urubamba, once again and turned eastward for a short walk into the hydro-electric station and its train terminus. Many trekkers end their walk here and catch the train for a 40-minute ride into Aguas Calientes. We joined the throng of waiting trekkers and other visitors for lunch at a railside restaurant, but our plans were different; we chose to walk the last 6 km along the gentle grade of the railway line. The train wasn't due to arrive for another two hours and we would be in town before it.

Farewelling Javier, Valerio and Ephraim, who took our gear by train and then continued on to Cuzco, we set off along the train line from the hydro-electric station. Not long after, a quick short-cut brought us up through a coffee plantation to reach the main Cuzco-Aguas Calientes line. From here it was but a long stroll along the train track, as it slowly spiralled its way through the dense vegetation of the steep Urubamba Canyon, pushing deeper into the Machu Picchu Reserve. The cloud that had been hovering about since lunch gradually thickened above us into a sombre grey mass that threatened to rain on our parade.

Eventually we left the railway to follow a dirt road for the final kilometre into Aguas Calientes, a booming tourist town that has cashed in on the popularity of Machu Picchu. It was a work in progress, with new hotels and apartments under construction everywhere and a railway line down the main street, while every second door seemed to house a restaurant or souvenir shop with a tout out front to drum up business.

We were off before dawn, strolling down the road from Aguas Calientes to the start of the climb up to Machu Picchu - the climax of our nine day trek. The sheer rock walls along the edge of the Urubamba River vanished into the clouds; somewhere above were the mystical ruins of the Incan "lost" city, but to reach them we first had to climb over 1700 stone steps. We crossed the river and climbed up through the dense humid forest, crossing many times the switchbacks of the road access as we took the direct and steeper trajectory.

The rain soon stopped, but the gently swirling fog and mists remained as Felix guided us around the maze of fascinating streets, buildings and terraced gardens, explaining their purpose along with the history, religious beliefs and customs of the quechua people at that time. The eerie mists created an appropriate ambience for a place whose origins and demise also remain shrouded in mystery.

The people of the Incan empire were brilliant stonemasons and their skills ensured that the houses, temples, walls, watercourses, observatories and other features of this site remained for 400 years hidden in the jungle growth of Machu Picchu, before being rediscovered by science in 1911. Slowly, as we wandered through the various sectors of the the site, the mists cleared more and more, never quite leaving, but gradually revealing the ruins in their totality. It was not the Machu Picchu of postcards that we visited, but an eerie and enigmatic Machu Picchu, where the ghosts of the past seemed closer in the mists.

After visiting the ruins, to prove our gluttony for punishment, we headed off across the upper agricultural terraces to join up with the old Inca road and climb another 250m to Intipunko - the Sun Gate - entry point to Machu Picchu from the south. The cobbled stones of the old road were lined with brightly coloured flowers of orchids and cloud forest shrubs, as it wound around the sheer edge of the Machu Picchu mountain.

The large fruit-eating guan

The tiny nectar-sipping picaflor

After five hours of exploring this amazing place, we declared our trek officially finished and headed back down to Aguas Calientes by bus, sat in the plaza to watch the world go by under the stern gaze of a large statue of the Inca, and caught the train back to Cuzco.

It had been one of the best treks we have done, twice down into the depths of a canyon, twice across a high alpine pass, traversing landscapes ranging from semi-desert to alpine grasslands and dense cloud forest, getting a feel for life in the remote Andean villages and for the history of ancient empires.

Thanks Felix, for being an excellent guide, to Javier, Valerio and Ephraim, the supermen who carried all our gear from canyon floor to high mountain pass twice over, and to all five for being such friendly and amusing companions on the trek.