Last weekend I climbed Volcan Agua.

It towers over Antigua at 3,700 metres. I climbed it with a group of foreigners who are also studying Spanish at my school.

First of all I had to get some equipment, because as many of you no doubt know I am not much of a hiker. I went to the market and bought a little daypack. It was $5 and it was bright yellow with Tweety Bird on it. That was the best I could do.

We all climed onto a chicken bus, which is an American schoolbus repainted in bright colours and loaded with as many people as can fit. We rode it a short distance to Santa Maria de Jesus, a little town at the base of the mountain. Here I learned from one of our guides that it would be supercold at the top of the volcano, so I bought a fleece in the market. The market was run by Mayan women, all decked out in their excellent clothes, speaking Cachiquel - if that's the right spelling - one of several indigenous languages.

Anyway, we started climbing. At first it was pretty pleasant, tramping along in single file up a narrow path, with the forest thick all around us, occasionally having to move aside for a farmer and his horse, loaded with chopped wood or crops of some sort.

It wasn't long, however, before I began to wonder how on earth I came to be in such a place, engaged in such an activity. I still don't understand it, but I guess everyone else was going and I didn't want to miss out. When the reality of climbing for six hours, then sleeping on the ground in a borrowed an inneffective sleeping bag began to dawn on me, I must say I started to feel worried.

But I carried on, chatting away and playing word games with these funny Australian medical students, Lachie and Andrew. Our guides weren't such terrific climbers themselves, and liked to stop quite frequently for refills of food, cigarettes and rum, so I was pleased about that. One of them, Rafael, was especially keen on rum. He was supposed to be our protector, and he had a large machete in his belt. There are bandits in the hills sometimes, but I'm not sure what Rafael, who was little and stout and clearly peace-loving, was going to do about them if they appeared.

Anyway, I was enjoying the exertion up to a point, but after more than five hours, I had well and truly had enough. But I thought to myself, at least I'll be pleased when I reach the top.

When we about 500 metres from the crater, though, things got really bad. There was a mist settling over the volcano and it was getting cold. At the same time, I was starting to feel very strange. I was breathing, but it didn't seem to be working the way it usually does. I was dizzy and I started to feel queasy. Rafael had to take Tweety because I couldn't carry him anymore.

When I saw the concrete bunkers we were to sleep in I realised the full extent of my folly. We spread some thin, greasy mattresses we found over the concrete floor and I had a few swigs of wine but none of it helped. I lay down, despondent, and tried to sleep but there was no chance. My hipbones were digging into the ground and I was disturbing my roomates, who were all huddled in together in their sleeping bags like a bunch of little grubs, with my half-delirious wimpers of distress.

At around 3am I started spewing, which provided no relief from the nausea.

The next day there was a magnificent sunrise but I felt like death and couldn't enjoy it. I lay back down.

I didn't know how I was going to get down the mountain, but somehow I did. After a few hundred feet I was back to normal, although very tired. So tired, in fact, that I managed to sleep all the way home on the chicken bus, wedged between my housemate, Didrik, and a farmer, on a seat for two.

I had a snooze back at the house, then Didrik and I met the Australians for a Trivia competition at the Irish pub. This cheered me up no end, as we won, and used our winnings to shout beers for the other teams.

I went to bed earlyish, but was woken just after midnight by a tremor! I was quite excited about it. The whole bed shook, and I could hear the town shaking, and the house seemed to shift from side to side. My bus driver today said he thought it was pretty strong, but that they have about five or six tremors like that each year.

The next morning at 4am I left for Honduras.