Two triumphs of the 20th century, for just pounds 9.30 return

Britain's most inspiring theme parks are at opposite ends of the Cambrian Coaster railway.

This week I have visited three theme parks. Yet the only "real" one, Thorpe Park, came in a distant third. Visitors emerge from this Surrey fun spot feeling tired and happy. But at mid-Wales's two thrill venues you will leave inspired.

The first great thing about Portmeirion and the Centre for Alternative Technology is that they are at opposite ends of the same joyful spectrum. At one extreme, a fine slice of scenery is enlivened in spectacular fashion with an audacious binge of creativity. At the other, man's humdrum activities are harnessed and rejuvenated by nature.

The second, and rather more practical attribute, is that they are at opposite ends of the same railway line. The Cambrian Coaster trundles industriously through rolling hills and skirts carefully around the rockier parts, forming the continuum between two opposing triumphs of the 20th- century for just pounds 9.30 return. Even allowing for admission fees to the two sites, you still spend less than on Thorpe Park.

Portmeirion

The Ordnance Survey map leads you to expect nothing special from the contours than slump into a modest fringe of estuary around the corner from Porthmadog. Yet on the ragged slope of woodland at Portmeirion, Sir Clough Williams-Ellis created a community as extravagant as his name. His idea was refreshingly blunt: "The Victorians had the idea of homes for fallen women. I thought it would be a good idea to have a home for fallen buildings."

Seventy years ago, the architect began to turn some nondescript lands of the gentry into a personal stash, capturing the best flourishes of artistic genius since the Renaissance. He was a man who could be trusted equally with preserving an entire Gothic portico (imported stone by weighty sandstone from Bristol) and with giving Bernini due respect while mimicking his sculptural twists and turns.

In the part of Wales where a chapel that diverges by two shades from the slate-grey norm raises civic eyebrows, he built up an architectural menagerie that begged to be either a film set or a tourist attraction. It turned out to be both.

Thirty summers ago, a cinematic cult was created on freshly mown turf. Not on the football field (though this was England's summer of '66), but on the neat lawn beneath the portico. Filming began of the series The Prisoner, whose 17 monochromatic episodes were set amid the pre-psychedelic confusion of Portmeirion.

Patrick McGoohan, like England's Bobby Moore, was known as number six. The small screen incarcerated The Prisoner in the Village, as an unwilling participant in the sort of script that can only have been dreamed up after a substantial quantity of controlled substances.

Today, at the on-site Prisoner Shop, what the plot meant seems less important as where or how. For instance: that chess game, which anyone old enough to have seen the '66 World Cup Final will remember. In the celebrated Checkmate episode, Patrick McGoohan becomes an unwilling human pawn on the central lawn. The giant-sized board was created by chequering the green lawn with white hardboard and allowing black-and-white television to do the rest. Every August, devotees are allowed a few days in which to recreate the setting and re-enact the spat between the Prisoner and the Rook.

Castles are a central feature of the kingdom of Portmeirion, with castellations and regal flourishes enriching any corner that might otherwise subside into the ordinary. Sir Clough was still twiddling with his supernatural creation in 1978, when he recorded the interview that underpins the audio- visual presentation for day-trippers. He reveals that he used tricks of scale throughout Portmeirion, and intended it to be "Just plausible - you can walk through every archway, but only just".

The tourist who diligently wanders through each such arch will be rewarded by dollops of a style which could be called Italian-lite. Slabs of pastel colour reverberate with Baroque trills and twirls, which in turn are imitated by the ice creams on sale. Kiosks seem to infect Portmeirion. One too many of Sir Clough's creations has been commandeered for commercial purposes, but the effect of the whole is as wildly ostentatious as his final words about his achievement are understated: "It may be of some help to those, like me, who want to recover some of the elegance of the past."

Sir Clough Williams-Ellis died in 1982. He was not a number, but a free man.

Portmeirion is a privately owned complex, for which day visitors (allowed 9.30am-5.30pm daily) pay pounds 3.20. The site is two miles east of Portmadog, and a 15-minute walk from both the narrow-gauge and BR railway stations in Minffordd. Call 01766 770228 for details of accommodation possibilities.

The Centre for Alternative Technology

At the Welsh riposte to the ills of late 20th-century life, you are inclined to paraphrase one of the more irritating current car commercials: everything you do is driven by nature.

At around the time Poland was busily knocking England out of the World Cup (1973), the biologist Peter Harper coined the phrase "alternative technology". It describes human behaviour, tools and devices that work with nature rather than against it. Luckily for Wales, a disused slate quarry in the middle of not very much was chosen to put this concept into practice.

Peter Harper is still working at the Centre for Alternative Technology, and has seen it grow into a fully-fledged tourist attraction; the Nineties knows no higher accolade. But unlike other theme parks, reliant on creating worlds that transcend our daily lives, the Centre revels in allowing the natural world to show off - to demonstrate how much brighter nature is than anything man has dreamed up so far.

The first solution offered by the planet is how to hoist you from road level to the 200-foot-high terrace where the action takes place. A reservoir takes advantage of the generous rainfall in Wales to provide power for the cliff railway.

"Hang on a minute - the computer's just weighing you". The man who takes your pounds 4.95 explains: the railway lifts visitors skyward in return for a little rainwater, assisted by a silicon chip. If you load one of a linked pair of carriages with enough water, its descent will force its partner up. The trick is to save water, which explains the computer. No Luddites here; the 20th century is embraced whenever it can help reduce the rate of global attrition.So you can phone Australia from a British Telecom booth that draws all its power from the sun and the wind - it sprouts a shield to soak up solar rays, and a turbine benefits from the not-inconsiderable breezes that are a climatic feature here.

In the cafe, you might recover after nature's exertions by ordering apple pie with honey. The corn for the flour has been cultivated with the help of natural alternatives to chemical pesticides.

The honey, meanwhile, is straight from one of the attractions: wild bees shun the need for artificial honeycombs by building their own hive inside a decaying beech trunk.

The next stage in the human digestive process is introduced with a poser: "About 400 million years ago, the first land animals came out of the sea. Unfortunately at that time there were no toilets. Animals just had to drop the stuff right there on the ground, and they've been doing so ever since. So why isn't the whole world several miles deep in prehistoric poo?"

The answer, of course, is biodegradability. You find this out while reading the walls of the WC, a hut which is poised above a pit whose agricultural value is enhanced with every visit. The resulting compost is used in the orchard to help cultivate fruits such as apples. What was in that pie again?

The Centre for Alternative Technology is three miles north of Machynlleth on the A487, served sporadically by buses. Machynlleth itself is served by trains from Birmingham every hour or two. Rail travellers can claim a 10 per cent reduction on the normal admission of pounds 4.95.

The Centre opens 10am-7pm daily in summer. Call 01654 703743 for further details, and for information on courses.