This was it. The big one. A trip a year in the planning (and a blog entry over a month in the writing). The first thing we booked after we bought our round the world tickets. The infamous Inca Trail.

It was with no small amount of trepidation that we shoved our packs onto the bus at 5am and clambered in after them. The Inca Trail is a 4-day trek into the heart of the Andes. We would be hiking up and down mountains, mostly at altitudes of over 3000m above sea level.

Luckily we had a great group to make the journey with. The night before we set off, we all met up for the first time at the company's offices in Cuzco for our briefing. (The company was called SAS. Meeting up for a 'briefing' at 'SAS HQ' did nothing to assuage our fears about the intensity of the forthcoming trip!) We were a group of 8. Pete, Claire, Sarah and myself along with 4 other Brits – a honeymooning couple from Leeds, Sammy & Martin; and two fellow Londoners, Iona and Jennifer. The British humour at the end of a hard day's hiking definitely helped keep our spirits up, although I think it may have baffled our guide Justino, who along with our 11 porters and cook were responsible for keeping us alive over the four days.

Day 1: This may be harder than we thought...

After a 5am start and an inauspicious flat tyre on the outskirts of Cuzco (mended with a bicycle puncture repair kit and some superglue) we arrived at the start of the trail, feeling ready for anything with our newly-purchased hats and walking sticks. 20 minutes after setting off this confidence was evaporating as fast as our Camelbaks. We had been walking up what we would describe as a steep hill since we had entered the park and were beginning to feel the strain. It didn't help that every minute or so we had to stand aside to watch packs of porters trot past, carrying bags bigger than themselves, wearing knackered plastic sandals on their feet.

At least we had some lovely scenery to distract us. We were walking up a steep-sided valley, with the roaring Urubamba river below us and a train line the other side – the same train that would carry us back from Machu Picchu in four days time. Flowering cactus and trees draped with cobweb-like epiphytes lined the dusty path.

All along the trail that first day we passed farms and small houses, each with a stall out front selling the hiking essentials – Coca Cola, cigarettes, chocolate and crisps. Sitting to catch our breath in one of the villages we watched a woman grinding corn with a large millstone whilst dogs played around her in the dirt. A cockerel started giving Sarah the evil eye. The only evidence of modern life was the empty chocolate wrappers and coke bottles on the ground.

After stopping at the village, the path took a turn for the worse. The last hour was much steeper and took us up onto a plateau of dense forest that wouldn't have been far out of place in Borneo, except for the llamas that occasionally stumbled past in front of leathery looking ladies in colourful skirts.

When we eventually arrived the campsite was basic, but made liveable by the hard work of the porters who had clearly got there there several hours before us. All our tents had been put up including the dining tent for 'Happy Hour' – biscuits, popcorn and hot chocolate have never tasted so good (even after the disappointment of learning that Happy Hour did not entail booze).

Day 2: Introduced to us as the 'Challenging Day', it definitely lived up to its reputation.

SAS like to make day 2 longer than the other trekking companies, opting to set up camp for the night about 10km further along the trail than all the other groups. This resulted in a head start on day 3 that got us to the final campsite by lunchtime – perfect for first dibs on the only hot showers on the trail and a rest before day 4. Had Justino & Co known how day 2 would pan out I'm sure we would have foregone the showers to avoid the afternoon's trekking...

We were woken at 5am with cups of mate tea and bowls of hot water outside our tents to wash ourselves. I could definitely get used to being waited on like this! Breakfast was a feast. Mario the cook served up pancakes as well as porridge, toast, biscuits and hot tea and coffee - fattening us up for the kill.

The first two hours of day 2 were probably the hardest of the whole trip. We had camped about half way up a mountain, at a plateau from which the track gently but inexorably curved upwards to a saddle known as 'Dead Woman's Pass'.

At 0630 we set off, climbing through a parrot-infested rainforest, past waterfalls and fast running streams. With my headphones in and my favourite embarrassing girlie-pop on loud, I paced off ahead of the group to try and get myself an early lead (not that it was a competition, but...). After 20 minutes of Ellie Goulding, pleased at finding myself alone ahead of the rest of the hikers, I stopped for a break. Then to my horror just behind me appeared a family of three Peruvians – a man, a child of no more than 10, and a weathered little woman who was breast feeding a baby whilst simultaneously prancing up the trail past me quick as a flash. Shamed, I promised myself that I would redouble my efforts, and resorted to drugs to help me do so. Shoving a fist-sized wadge of coca leaves into my mouth, I set off once again.

As the family receded into the distance ahead, the rainforest thinned out and gave way to 'puna' grassland and then a moor-like landscape of rock and heather. Suddenly you could see the craggy mountain tops above, and clouds shrouding their summits. The air seemed colder and thinner. I chewed more coca and carried on upwards.

We made it to Dead Woman's Pass at 10am. At 4200m ASL it was the highest point on the trip, just below the snowline. I don't think any of us have ever done that much exercise before 10. Even the porters sat down to have a rest and take in the view of the ascent we had just made. The campsite we had left that morning was barely visible through the cloud and forest, and the path we had climbed looked like a tiny silvery snail trail on the side of the mountain.

From there it was all downhill to our lunchtime campsite stop. Unfortunately Sarah's knackered knees mean that we were slower going downhill than up, so we arrived at the site about an hour after the rest of the group. 5 minutes after finishing lunch half of the group had fallen asleep on their benches, exhausted after the morning's exertions.

We left most of the other tours behind at this point, heading off and upwards once again to our second summit of the day on a series of stone steps known as 'Gringo Hell'. As we climbed, clouds began to swarm behind us over the valley where we had camped for lunch. These clouds quickly darkened through grey to black, punctuated by streaks of lightning in the distance. The trail ahead of us also started to fade into a chilly mist, and whereas we were hot in our t-shirts 10 minutes ago, we now found ourselves fully zipped-up in our North Face jackets and still feeling the cold. Justino was looking a little nervous.

As we stood on our second 4000+m summit of the day, the rain started. With 6km of steep downhill track to cover before we reached our campsite, we set off down the other side of the mountain... straight into thick cloud that hid all but the next 5 metres of the trail from us. The rain got heavier, and a wind kicked up. Then the rain gave way to hail. And the hail got stronger. By this point Sarah and I were completely alone on the mountain, carefully edging down the slippery steps. Our gore-Tex had completely given up and we were soaked to the skin. Then the lightning began. I counted the seconds till the thunder: Flash.... RUMBLE: 5 seconds, FLASH CRACK, 1. My attempts to lighten the mood by whistling 'Singing in the Rain' didn't seem to help Sarah much, but then I think she was too busy concentrating on keeping her footing on a trail that had now totally vanished beneath a carpet of hail and rainwater. The 'Inca Trail' was now more like the 'Inca Rapids'.

About halfway to the campsite we found Justino waiting for us, sheltering in a cave and looking a little smug in a head to toe plastic poncho. With his encouragement we pushed on through the hail, walking as fast as we could, the carrot of hot food ahead balanced by the stick of potentially being stuck on the mountain in the dark. Two hours later, we were beneath the clouds again, and could just see our campsite lights flickering over the other side of the valley. After another hour we made it to our tent just as the last light left the mountains. Justino looked visibly relieved. Happy Hour was supplemented with a bottle of rum that we supped in the dining tent, steaming in our wet clothes.

Day 3: Aching legs & stunning views

What a difference a day makes. After our morning mate tea, we climbed out of our tent to find ourselves surrounded by scenery. Snow-capped mountains in the distance, a carpet of forest beneath us, and the Incan fortress Sayacmarca precariously positioned on a mountain ridge opposite.

We skirted along a mountain ridge soaking up these views all morning before dropping down over the other side into Puyupatamarca, a religious site that used to be one of the last stops on the ancient route to Machu Picchu. It was here that the first tourists – pilgrims – used to purify themselves before making the final stage of their journey to the famous city.

Ddead ahead we could see Machu Picchu mountain – the city lay on the other side though, tantalisingly close. Far below the Urubamba river ran past us and around the mountain, and below us to the left were the terraces of Intipata. Intipata was essentially a farm, one of several built into the impossibly steep slopes of surrounding mountainsides to supply the city of Machu Picchu with grain, vegetables and fruit. Thinking about the effort needed to build these terraces, so far from anywhere, in a jungle halfway up a sheer cliff gave us an idea of the power the Empire must have wielded in its day.

The route from Puyupatamarca to Intipata was all downhill through high jungle. As the path was good, I decided to run. It was awesome – a real Indian Jones-esque adventure. I ran down the original Inca steps and pathways, past moss-covered guard-posts on my left and sheer drops into the jungle on my right. Clouds of blue butterflies scattered in the morning sun.

We reached the final campsite by lunchtime, and as promised were first to enjoy the heavenly hot showers (still, not sure it was worth enduring the hail and thunderstorm). The campsite had an actual concrete building for us to eat inside, and even had a small bar selling overpriced beer which we invested in that evening.

Before that though, we took a short stroll round the corner from the campsite into one last Inca site, Chachabamba. This was another farm like Intipata, but with its amphitheatre-shaped terraces and large temple complex was even more impressive. It started to drizzle as we walked around so the rest of the group soon retreated to the bar. I stayed out a little longer to explore the buildings and terraces on my own, and was soon the only person there. Then, as the rain came in, the site's irrigation system suddenly started up – water flowing down stone channels and pipes, just as intended when they were carved over 500 years ago. I followed the pipes around the entire site, tracing them from the terraces they watered back up the hill, through the temple buildings only to have them vanish into the undergrowth alongside some overgrown steps that led up into the forest. Looking up at the steps, I decided I had indulged my Indiana Jones fantasy enough, and walked back to the bar through the rain.

After our final Mario-cooked meal and a number of Cusqueña beers we decided to play a friendly game of shit-head. Due to the addition of a number of interesting Peruvian rules this game soon degenerated into a shouting, card-throwing, beer-drinking huddle that raged on long after the rest of the bar had emptied out.

Day 4: All worth it!

Like hungover kids at Christmas, we woke up early with slightly fuzzy heads - 3.30am. Everyone at the site does the same, and queues up at the entry gates to the last stage of the trail in the hope of being the first to see Machu Picchu at sunrise from the Sun Gate. Unfortunately, as many groups join the trail at the last campsite (having caught the train up from Cuzco and avoided the trekking), this last section of the trail is the most crowded and has the slowest groups on it. These groups also tended to be filled with people who were most inclined to stop and take photos. Progress was slow.

It was all worth it. At 5am we reached the Sun Gate, and looked down on the city of Machu Picchu, sprawling over the mountain beneath the gaze of the Waynu Picchu summit. Wisps of cloud came and went, arcing over the buildings and terraces. The whole trek was worth it for that one view.

Machu Picchu is often described as a ruin, which is a little unfair given that it's almost completely intact. It was built at the height of the Incan Empire around 1400, abandoned a century later to the approaching Spanish, and 'discovered' by the archaeologist Hiram Bingham in 1911. Locals find this 'discovery' a bit much, given that the site was well known to them, and in fact a farming family had been making their living amongst the overgrown buildings for as long as they could remember.

Regardless of who found it when, the city is incredible. If we were impressed by the terraced farms built on the sides of mountains, we were dumbfounded by the scale of Machu Picchu. This feat of engineering was even more amazing given that there were no slaves in the Incan Empire - all of it was built with voluntary labour.

Machu Picchu was the religious centre of the entire Incan Empire. Its auspicious position above the Sacred Valley, with a panoramic view of the surrounding mountains apparently made it an ideal location to commune with the gods. The many temples here all served this purpose, and the city's layout itself was meant to symbolise a condor - the mythical link between heaven and earth. The Temple of the Sun is probably the most famous building in the city. It was built to have a precise relationship with the Sun Gate, so that at dawn on the summer solstice the sun's first rays shine through the gate and strike the temple's altar.

The benefit of having hiked to Machu Picchu is that you get to explore the site before it is opened to the bus-loads of tourists that arrive directly from Cuzco. Along with only a hundred or so other hikers, we had the city to ourselves for the first couple of hours. Justino walked us around the site and explained some of its features, but to be honest the best part of the trip was just being able to wander around the massive buildings and temples. The city would have housed about 500 people in its heyday, mostly important religious families, which was about the number of tourists which had arrived by noon. It must have been a bustling place!

Before we left to catch the train back to Cuzco, Justino offered us the opportunity of one last climb – up to the summit of Waynu Picchu, a group of buildings perched on the very peak of the mountain. The rest of the group weren't too keen, so Pete loaned me his electrolyte-charged Camelbak and I attempted a solo-ascent. The authorities only allow 400 people to climb Waynu Picchu each day, but Justino put one of my 20 peso notes in the right hand and I was snuck in. The climb up was the steepest of the trip – steps hewn out of a sheer rock-face – but thankfully it wasn't too long a hike. As I stood hyperventilating on the summit, the 360° view of Machu Picchu and the mountains of the Sacred Valley was unforgettable.