Holidays to the final frontier

Perhaps you're beginning to feel as though there's nothing left to achieve in this life, even if you've hardly achieved anything.

Somebody somewhere has already got there before you and done it all. There are no real adventures left. Everything has been made civilised and safe. All the endurance milestones have been reached. Grannies bungee-jump for charity.

Space, traditionally considered the final frontier, is off the menu for the common man now that spoilsport multimillionaire Dennis Tito has bought his way into the record books.

So what can a loser like you do? Well, don't lose heart. Pickings are slimmer than they were, certainly, but there's still plenty of frontier down at the bottom of the barrel, challenges bold and adventurous, as well as crazy and dangerous, and all of them as utterly pointless as ballooning round the world. Perhaps none of them are as great as going into orbit, but beggars can't be choosers. Here's what's left:

Swim with sharks on the World's Most Dangerous Dive. The terminally foolhardy will be glad to hear that there is a place where you can swim with sharks on purpose. Cocos Island Marine Park, 300 miles off the coast of Costa Rica, contains more sharks per cubic metre of water than anywhere else on the planet, including white tips, 40ft whale sharks, Galapagos sharks and hammerheads. What's more, there are plenty of tour operators willing to take you out there in a boat and heave you over the side into the shark-infested foam. There are also eagle rays, mantas, parrotfish, moray eels and tuna, but it wouldn't pay to get too distracted. A perfect day out for anyone who has grown bored with being stomped to death by elephants.

Climb the World's Tallest Tree. Who says you can't have it all? Find your inner child in the most death-defying manner possible, by shinning up the world's tallest coast redwood in California. There seems to be some dispute about which redwood is actually the biggest and, like all big things, they seem to be getting smaller. The cleverly named 'Tall Tree' in Redwood National Park once stood at nearly 368ft, but a storm lopped off the top 10 feet.

The nearby National Geographic Tree is also a contender at 365ft 6in. Today, the Mendocino Tree in Montgomery Woods, near Ukiah, California, is generally recognised as the official World's Tallest Tree. But, unfortunately, it has already been climbed by the guy who measured it, botany professor Steve Sillett, whose tape measure spooled out 367ft 6in, more than twice the height of the Albert Memorial. Of course, you could always be the first non-botany professor to climb the Mendocino Tree, but there are a few other challenges to overcome: its exact location is a closely guarded secret, and the first branch is 190ft from the ground.

Climb an Unclimbed Mountain. Surprisingly, there are quite a few major challenges left in the world of mountain climbing. Several Himalayan peaks in the 6,000m to 7,000m range have yet to be conquered, but Gangkar Punsum, a peak on the Bhutan/Tibet border, is recognised as the tallest unclimbed mountain, at 7,541m. Of course, there's a good reason why nobody's got to the top of it yet: it's very difficult. There have been attempts in the past, but Bhutan, the self-styled 'Land of Gross National Happiness', currently forbids expeditions on Gangkar Punsum. It is possible that the Chinese may open their side of the mountain to climbers one day.

Go Deep. Mankind may have conquered Everest, both Poles and the Moon, but the race to the centre of the Earth proceeds with painful slowness; nobody has even got to the level where the Mole People live yet. In 1989, some cavers known as the Groupe Vulcain descended 5,256ft into a big hole called Gouffre Jean-Bernard in France, setting a new world record by travelling just 1/100th of the distance to the planet's molten core. Apparently, they never even got to the bottom of this particular cave, so there's an easy record there to be snatched by someone with a slightly longer rope.

Hang outin the World's Most Dangerous Place. Officially, Sierra Leone is the most dangerous place on Earth, at least in terms of incidents of man's inhumanity to man per capita per annum. The Guinness Book of World Records cites the country's annual death rate of 25.1 per 1,000 people, along with the average life expectancy of 41.5 years, as the world's highest and lowest respectively. Foreign Office advice on Sierra Leone could best be summed up as 'don't go there'.

Founded in 1787 as an experimental community of freed slaves, Sierra Leone boasted a 90 per cent death rate in its early years, so, relatively speaking, things have improved dramatically. However, years of fighting between government-backed mercenaries and flesh-eating (yes, that's right) rebel forces have made it less than tourist-friendly. Of course, if you live there, you know this already.

Visit the Remotest Place on Earth. Judging remoteness is a fairly subjective game and once you've fallen asleep on the Tube and woken up at Cockfosters, all things are relative. For our purposes, the most remote place is the spot on the ocean which is furthest from land in any direction. This turns out to be a point in the South Pacific, 47 degrees 30 minutes south, 120 degrees west, which is at the centre of a landless, eight-million-square-mile circle of water. The nearest dry land, 1,600 miles to the north-west, is Pitcairn Island, itself no steaming metropolis. In fact, with a population of about 50, Pitcairn has the distinction of being able to offer a small biography of each and every citizen on its website. If you felt like paddling south, you could head for the tiny Norwegian protectorate of Peter Island, but by the time you've got there you may as well carry on to Antarctica.

Jump into the Biggest Underground Lake. In terms of getting away from it all, you might like to try being in the middle of a big body of water and deep underground at the same time. Surely here you will be safe from people with clipboards asking you to switch electricity providers. Drachenhauchloch (Dragon's Breath) Cave in Namibia contains the largest known underground lake, which was only discovered in 1986. The lake has a surface area of 6.45 acres, lies 217ft underground and is itself 276ft deep. Whatever it is you're looking for that's somehow missing in your life, chances are it will be right down at the bottom.

Befriend a Lost Tribe. There are still a few indigenous peoples out there who, because of either remoteness or unfriendliness or some combination of the two, remain largely untouched by Western civilisation. Meeting them could be your last chance to be promoted from the IT department to the post of Living God. The most likely candidates are:

1 The Liawep of Papua New Guinea, unknown until 1993. The 79-strong tribe worships a rock they carry everywhere with them. Advantages: said to be very impressed by Western comforts such as tea, salt, buildings and knives. Drawbacks: the Baptists have already got to them and had a word about the rock.

2 The Naua Indians of Brazil were thought to have died out in the Twenties, but then 250 of them turned up last August to lay claim to some national park land. Advantages: the Baptists haven't moved in yet. Drawbacks: even after 80 years in the wilderness, they seem to have a clear idea of their rights.

3 The Sentinelese, the remotest of four tribes of the Andaman Islands, in the Bay of Bengal. Nobody knows much about them. Advantages: as a pre-Neolithic people, they are unlikely to have seen the cut-and-restored-rope trick. Drawbacks: the last folks who tried to get to know them, back in 1974, had their boat showered with arrows.

Be the Toughest Man on Earth. You'd think you might have to travel far and wide to secure the title of Toughest Man on Earth, but the annual Tough Guy competition is held right here in the UK, as it has been every winter for the past 16 years. Run by Billy Wilson, a Wolverhampton farmer known as 'Mr Mouse', the event consists of a gruelling cross-country run followed by an assault course. The 5,000 contestants who regularly take part are obliged to crawl through narrow pipes, through thick freezing mud, over walls and under razor wire, as well as swimming 12ft through an 'underwater tunnel'. A new obstacle is added every year. Last year somebody died. Suffice to say the Tough Guy competition makes the London Marathon look like a trip to B&Q.

Find North London's Lost PC World. Somewhere far out on the North Circular, in the place called Staples Corner near Neasden, not that far from Ikea - yes, yes, you know the place! - there is said to exist a branch of PC World. It's in the telephone directory and everything. In fact, you can see its large sign briefly emerging from the mist just as you exit at the junction with the A5, but then you are immediately herded onto a roundabout, forced up and over the motorway on a spindly bridge and down onto a road which leads to the deserted loading bay of a Tesco. No matter how you attack the junction, you can never quite reach the car park of this PC World, and you must get back onto the North Circular going the wrong way and travel some considerable distance before you can exit for another attempt. Perhaps PC World is not part of 'our' world, perhaps it occupies a small wrinkle in the space-time continuum, or perhaps, like the magical village of Brigadoon, it appears just once every 100 years. In any case, you may go to Staples Corner and seek this PC World, and if you find it, I need a new printer cable.