"Kathmandu? Well, it's just a shit-hole really isn't it?" This, at least, was the opinion of one British trekker whom I met just after breakfast on my first morning in the city. For someone who came here for the mountains, it's an understandable attitude - Kathmandu is the antithesis of everything that brings most travellers to Nepal. It's dirty, noisy, crowded and so polluted that after three days here my throat feels like I've just chain-smoked five packs of unfiltered high-tar cigarettes. But I still don't think that the city should be dismissed as just a place that has to be endured before heading off into the Himalayas.

I found a guide to get me orientated with the city on my first morning. More accurately, he found me; he was one of the many self-styled tourist guides who tout for business around the main hotel districts. They're not aggressive, just persistent, their standard technique being to just follow the tourist around, pointing out some landmarks and then asking for money. It's easy enough to get rid of them as long as you make it very clear from the start that you're not going to give them any cash. But this guy - Jiri was his name - seemed to know what he was doing, and I figured that going around with one guide would keep the others off my back.

Jiri's little tour took me to: a Shiva shrine with fresh blood outside where a buffalo had been sacrificed; a temple to Ganesh, Shiva's son, who has an elephant's head and is associated with luck and prosperity; and a residential courtyard where life goes on away from the chaos of the streets. Entering through an archway low enough so that even I (5'6") had to stoop to get through, the cacophany outside faded into the distance. Children washed clothes at a handpump, while two women left an offering at one of the small shrines built into the brickwork of the buildings. It was surprisingly tranquil.

Back outside the courtyard, we walked down towards Asan Tole, one of the main squares in the heart of the city. We passed rows of hole-in-the-wall shops selling fruit, meat (dead and alive), David Beckham football shirts, huge bags of rice, Coca Cola, beer, medicines, herbs, Buddha statues, and electrical goods in various states of repair. Five or six live chickens, all tied together by their feet, were being carried along the street draped over the handlebars of a bicycle. A man carried a fridge on his head - or rather he carried it sherpa style, on his back, supported by a band around the forehead. Hawkers approached me trying to sell anything from tins of Tiger Balm to snake charming demonstrations. Jiri was particularly disparaging about a woman who tried (successfully) to sell me a small shoulded bag. "That woman Indian, not Nepali." he said. "She is mossa, you know, prostitute, she have eight children, really, I am not shitting you." Maybe he was just annoyed that I was paying him less than I paid for the bag.

After lunch (and after my guide had found another couple of tourists to follow around), I walked down towards the central Durbar Square. "Durbar" means "palace", and the old royal palace overlooks the square, which also contains some of the most important temples in the country, and is the focus of many of Kathmandu's festivals. The streets in this part of town were even more crowded, and I was surprised not to see a single accident. The roads are narrow, usually unpaved, and since there are no pavements everything fights for the same space: pedestrians, bicycles, dogs, motorbikes, cars, vans, and those horrible little three-wheeled autorickshaws that fumigate the narrow lanes with clouds of noxious black smoke. There was little traffic in the square itself, but it was still crowded; as part of the Dasain festivities, the king was due to make an appearance, and the steps of the Maju Deval temple were filling up with onlookers. Given recent events in Nepal, I decided that I didn't really want to be too close to the procession (just in case...), so I returned after His Majesty had left.

The square, of course, is visually stunning, with so much craftsmanship being packed into a relatively small area. But it's also interesting for the insight it gives into religious life in Kathmandu. The Nepali calendar has many festivals, and each temple in Durbar Square plays a role in one or more of them. During Indra Jatra (usually in September), beer is poured into the mouth of the White Bairab statue (a fearful manifestation of Shiva who likes a good punch-up, and for some reason is associated with beer). Men then scramble to grab a drink of the beer, which emerges through a tube. This is also the time when the Kumari Devi - a young girl worshipped as an incarnation of Shiva - makes a rare public appearance. Usually she stays inside the Kumari Bahal, the house in Durbar Square decorated with beautifully intricate Newari wood carvings.

Despite the grime and chaos of Kathmandu, it's been the little random observations that have made my first few days interesting: the fruit stall set up behind a pile of decomposing rubbish; the children making offerings of food at a tiny street shrine; the flocks of paper kites flown from rooftops and windows all across the city. In contrast, the tourist district of Thamel is increasingly reminding me of Camden Market in London: the stalls selling tacky T-shirts and hats; the furtive hashish sellers; the bookshop offering spiritual enlightenment where "Pendulum Dowsing" sits next to "A Brief History of Time", "The Alchemist's Handbook" next to "The Origin of Species", and "The Life of Pi" next to "The 7 Habits of Highly Effective People". For me, the city is summed up by the ever-present smell of the place, which seems to be a mixture of vehicle emissions, incense and excrement.

For the next couple of weeks I'll be travelling with a small tour group. First, we spend a week on the Helambu trek, then continue to Bantipur and Pokhara. I hope that the mountain air will clear my lungs of all the diesel fumes that I've been breathing in Kathmandu.