Back in El Chalten, we were earlier than expected, but not early enough to get a different bus, which meant a few hours getting to know the bus station. The only consolation was that Cerro Torre never cleared that day. That night we were back in El Calafate, in a new hostel this time.

As usual with trips it was an up-at-the-crack-of-dawn start, piling into a coach full of tourists. There is only one company that actually allows you to walk on the glacier, Hielo y Aventura, and the coach couldn't have had more emblems on it. It was already one of the most touristy things we've done as I haven't been on a coach (as opposed to a minibus) since the Aircoach that took me to Dublin.

Our tour guide told us he loved Thin Lizzy, so when he heard we were Irish he was delighted. Sean ensured he wouldn't forget us by telling him an anecdote about Phil Lynott that he hadn't heard before. When Lynott was asked what's its like to black and Irish, he replied "Like a pint of Guinness."

After his El Calafate and glacier spiel, our guide started fielding questions and on the second or third question the bus driver spoke to him. The guide quickly said he'd answer the question in a few minutes and sat down. Next the light classical music playing in the background was turned up and as we turned a corner, the music built to a crescendo. Just then, from around the edge of the cliff, we got our first view of the Perito Moreno glacier, to the sound of cymbals and drums. Corny just doesn't describe it. Even the guide knew it, as he stood back up with a sorry-for-the-cheesiness smile.

Next to the visitors centre is a maze of a walking platform, designed to give you as many viewpoints of the glacier as possible. It's also big to accommodate the masses of visitors that arrive when rupturing is going to happen. Rupturing starts when the ice advances so far that it meets the land, splitting the Lago Argentino in two. The water level on one side of the ice then rises, causing huge pressure to build up due to the height difference, eventually breaking the ice in a rupture. People even camp nearby to be able to see the awesome event.

But back to what we actually saw. To say this thing is big isn't quite putting it right; the stats I am about to fire out don't quite capture this thing. You can read about it, as we did, but it's hard to visualise. It's truly something you need to see to believe.

The glacier is on average 74m high, but is higher in the middle due to the compression from the sides. The glacier is always in a state of change, either advancing or receding, and contrary to the global warming theory, Perito Moreno is currently advancing, although no one knows why. The glacier is 30km long, 5km wide and sits in a valley that it has carved itself over thousands of years. It's a rich blue colour at the base and bright white at the top - thank you, refraction of light.

We got plenty of photos taken, including the obligatory panoramic shots. All the while we were waiting for some calving. Calving is when the massive chunks of ice break off the front of the glacier. The glacier is constantly moving, although really skowly so it doesn't look like it, so the calving happens all the time. Its not unusual for the icebergs to be as big as your house and the sound that accompanies it is akin to thunder.

For a video of a Perito Moreno calving, watch this clip:

http://www.youtube.com/watch?v=pcBdZkJ6DjE

We did not see anything this spectacular.

Fortunately we did get to see calvings, albeit small ones and typically only heard the sounds of a big one from behind some trees. A few seconds later and the ice had sunk into the water and a large wave was all that remained. The thunderous noise is nearly constant, but you just need to be in the right place to see it.

Thankfully we got to see a larger calving a while later, while on the boat across the lake to the glaciers edge. Looking at it from the boat gives you another dimension as the ice towers above your head.

We landed on the other shore of Lago Argentino and hiked into the woods flanking the glacier. When we reached a little hut we stopped to get our crampons and harness, before hiking further along the edge of the woods, and then finally stepping onto the glacier.

We spent about three hours walking around on the glacier, including a lake side lunch stop. Because there are no paths and the glacier is constantly moving, no two groups walk the same area. There are lakes and streams flowing through and on top of the glacier, and it's not too stable either. As I was crossing a stream, the ledge of ice I was standing on broke away and for a few seconds I was floating down the river, but then the extended arm of a guide was in reach and I stepped back onto solid ground.

The landscape is quite contrasting. On the surface, everything is white, but look down a crevice or fissure in the ice and all you see is blue. With all the white, although we couldn't ball it up and throw it one another, it was as close to Christmas as we were going to feel, what with a Sydney Christmas ahead of us. Off in the distance, in the centre of the glacier, are jagged peaks of ice. But the edges we were walking on we're smooth. This is because the edges are being pushed into the centre, by gravity, which also means that the centre flows faster, making the front face if the glacier V shaped.

As we were on our way back, the guide was on a mission, but he hadn't told us about it. He was searching for a cave in the ice that had been formed by melting water, a cave that he'd heard about but not been to himself. He found it and we were all impressed. The walls were a deep blue colour and constantly dripping on us. The cave started off a bit taller than me but got slowly narrower, before there was a sharp drop and we could go no further.

As we're nearly back on solid, but brown and green, land, I felt a tug on boot, and the strap on my crampon had snapped. I had to make the rest of my way back very gingerly; with one shoe free to slip, a single wrong move and I could have ended up doing a very sore splits.

On the boat back across the lake, we were treated to Argentinian chocolate with Scottish scotch, served on the rocks - with glacier ice. Naturally, being Thin Lizzy fans, we managed to get two each!

As our trip draws to a close, we've seen some spectacular sights and the Perito Moreno glacier is one of the highlights. I would put it alongside Macchu Pichu and Iguazu Falls as the top things to do on this magnificent continent. But as to a favourite, I think I'm still deciding.