To the standard 7 year old's excuse of 'But the other boys told me to do it', my primary school teacher used to respond, 'And if they told you to go jump off a cliff, would you?'. Mrs Fawcett would have been very disappointed with me, as I stood there with a stick of dynamite in my mouth and a lit match next to the fuse...

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Walking through the town centre today it's pretty hard to imagine that Potosí was once the largest city in the world – bigger than London, New York or Paris. It still retains a little of this grand past, but not much beyond a few nice stone buildings and a pretty main square. The source of the town's wealth is the same reason that tourists visit it today – the silver mines of Cerro Rico.

Potosí used to be the most important mining town in the world. Having heard rumours of silver found in the area in the mid-1500s, invading Spanish immediately moved in and set their slaves to work digging. They hit the jackpot. Cerro Rico – Rich Mountain – soon became the jewel in the crown of the Spanish Empire, supplying the silver that fueled their imperial aspirations. Their Spanish Silver Dollars (more commonly known as Pieces of Eight as they were worth 8 of the old Spanish Reales) became so ubiquitous that they were used as a de facto international currency.

Millions of African slaves and indigenous tribespeople died working in the mines, which are now nearly depleted of silver. But even though all the easily excavated seams exhausted, over two thousand miners still venture down the tunnels every day, digging ever deeper to find silver and tin.

Cerro Rico is now mined as a co-operative, and we were told by the miners we met that this is a good thing as it means they only work for themselves. By all accounts, it's well paid work. A 12-hour shift down the mines, even as an unskilled labourer, can earn you as much as a week of standard above-ground work. All you need is a pair of boots, some gloves and a helmet and off you go. Still, I'm not sure all miners are so upbeat about their prospects - between accidents, silicosis and asbestos poisoning, the average life expectancy of a miner is under 50.

Not put off by a little asbestos, soon after arriving in the town Swills and I suited up in overalls, wellies and hard hats and set off to the miner's market.

Before we went down into the depths we stopped at a market to pick up supplies. We would be visiting a working mine, so the deal is you bring the miners supplies and they let you tramp down their tunnels and get in the way and take your photos. We bought booze, coca and dynamite. The favourite drink down the mines is Ceibo - a 96% abv spirit that is drunk mixed with juice or water. Coca leaves are chewed constantly to combat the low oxygen and long hours. We bought a bag for the miners and a bag for ourselves.

We went to a special store to buy the dynamite. Our guide demonstrated how stable the substance is by throwing it at us to catch. The look on the girl's face when she dropped the stick thrown at her was priceless... or I imagine it would have been had I not had my eyes closed, waiting for the explosion. We thus learned that dynamite only explodes if it has a detonator pressed into it. So we bought some of these too. At this point our guide suggested that it would make a good photo if we each put the dynamite, with fuse attached, in our mouths. I'll never understand why I did it. Mrs Fawcett's words echoed in my head as I flicked the lighter on and Swills took a photo. Madness. I regained my senses by the time we had bought the sticks and had to carry them into the mine – I put them in Swills' bag.

Up close, the mines look like any building site. Mud and puddles, diggers and rubble. Our bus dropped us next to a group of wooden buildings leaning against the hill around an ominous dark hole with twisted metal tracks leading out of it. It looked like the mine hadn't been used in a while. Then suddenly a dirty looking figure emerged from the darkness in front of a trolley loaded full of rubble. Whilst old, the mine was definitely still in operation.

Having flicked on our head torches and shoved fat wadges of coca leaves into our mouths, we formed into a line and entered the mine. We walked down the tracks, through puddles of water, under twisted pipes of compressed air and electrical wires. We were soon in complete darkness, using our lamps to watch out for the low wooden beams that held up the more shaky sections of the tunnel. Every now and then our guide would shout Aguarde! - Look out! - and we would have to press ourselves to the sides of the tunnel as a loaded trolley rattled past, pushed by another three miners – one at front to steer, and two at the back to push, all with tennis ball-sized lumps of coca tucked in their cheeks. We stopped one crew (Cost: one beer, one bag of coca) and asked what time they had started their shift. The wired-looking guy at the front blinked, then answered 'Medianoche' – midnight, 13 hours ago.

Having walked for about 20 minutes into the depths of the hill (and Swills having hit his head on beams about a dozen times), we veered off down a side tunnel and found a crew working at the rock face. They carried on working as we sat on the floor and our guide introduced each of them (including one 40 year-old miner nicknamed Rambo due to his big ropey muscles) and then set to work mixing the drinks. We started with a few beers, and then moved on to Ceibo & juice. Each round one person was in charge of pouring the drinks and we each drank from the same small cup in turn. Before we took a sip though, we had to pour some of our drink on the ground. Once for Pachamama – Mother Earth – and once for the safety and success of our fellow miners. The Ceibo was pretty rough stuff, so when the tourists were drinking Pachamama got a pretty sizeable offering – when the miners drank she only got a little taste. Even so, after a couple of rounds in the heat of the mines we were all feeling a little light-headed. This was when Swills and I both had a go shovelling some ore to fill a trolley. Not as easy as it looked, but then we probably hadn't had enough coca.

Feeling a little bit pissed and by now totally jacked-up on coca leaves, we said goodbye to the miners and wandered back down the tunnel. Halfway back to the surface we stopped and climbed up to another level through a crack in the roof and into a large chamber where we found a dusty old man sitting against the wall smoking a cigarette. This was Juan, the dynamite expert. With his 'supervision' (he sat, smoked and drank the whole time) our guide ordered Swills and myself to press a detonator into the end of two sticks of dynamite and attach a fuse. Again, why I obliged I can't really say. Sheer idiocy. Our guide then cut four minutes of fuse, lit the end, and passed the lit dynamite back to us. What happened then was like the opposite of pass-the-parcel, played at high-speed. The fizzing sticks of dynamite were handed very rapidly around our group for a tense couple of minutes, before our guide took them from us and clambered to the far end of the chamber where he hid them round a corner... DOOM! DOOM! The dull thud of the explosions came quickly, like someone clapping their hands around your ears, then there was a tense half-second while we waited, expecting the roof to come down on us.