Best of the stones: The ancient structures at Stonehenge are truly rocks of ages

You know Stonehenge, of course: a haunting silhouette from the past that stands gaunt and defiant on the chalky grassland of Wiltshire, just where the busy A303 and A344 meet. This inspirational stone circle, a triumph of the human spirit, was bequeathed millennia ago. It is now protected by English Heritage and forms part of a Unesco World Heritage Site.

Last year, almost 900,000 visitors stepped from their cars and coaches to get closer to the neolithic wonder. An enriching experience, set to become better still when a new visitor centre opens next year. It is tantalising, though, to be so close to the stones, yet unable to wander through them and wonder at the forces that brought them here. Since 1978, they have been off-limits because of worries about vandalism and erosion caused by rising visitor numbers.

How much more rewarding it would be to be able to walk unfettered beyond the "velvet rope" that keeps visitors at bay. Well, an average of 1,000 people a month are lucky enough to get up close for a personal experience of the stone circle. On a range of days throughout the year, people who book ahead can get access to the heart of the site, in groups no larger than 26.

I signed up for the last such tour in September – which is why at dawn on Monday, I could be seen cycling north from Salisbury station in order to make the appointment of 8am sharp.

A brief history of Stonehenge, I mused as I huffed and puffed, is an impossible task. Suffice it to say that around 5,000 years ago, a circular ditch and mound was created. The site's initial purpose seems to have been as a cremation cemetery. Perhaps half a millennium later, around 2500BC, standing stones were introduced – including the massive slabs topped by lintels that give Stonehenge its popular profile.

By the time the Romans arrived, the site had long lost its ceremonial significance – and spent most of the Christian era being regarded as about as much use as a pile of old stones. Yet in a remarkable early 20th-century conservation effort, a campaign succeeded in preserving the site, removing latter-day buildings and saving the signature site for the nation.

The 21st-century explorer needs the Ordnance Survey Landranger map 184, "Salisbury & The Plain". The place names provide a mix of excitement (Old Sarum, Druid's Lodge, Longbarrow Cross Roads) and foreboding (Breakheart Bottom). A gothic font pops up a lot, highlighting a remarkable density of earthworks created by ancient Britons as gifts from the living to the dead.

Stonehenge is just one element in an elaborate network of ceremonial sites scattered across Wiltshire, but it is by far the most prominent. When first they appear on the horizon, the raw reality of the stones makes you gasp – especially if you happen to be on a bike: Stonehenge is about 300 feet above sea level.

Everyone else on my tour had the good sense to arrive by coach: a company called Premium Tours has a regular day-trip schedule from London, which also includes Laycock and Bath. With a moment of trepidation, I stepped past the "No admittance" sign and on to the soft, springy grass, unwittingly triggering a faint mist of dew.

Like latter-day pilgrims, we followed the tour leader, Jason Ridgley, to the "altar stone" at the centre of the circle. Up close, you are overwhelmed by the scale of the construction: blocks of hard sandstone from 25 to 50 tons, quarried from the Marlborough Downs and dragged by weight of numbers and sheer determination around 4,000 years ago, to form a circle of 30 massive stones. They were topped, thanks to primitive but effective inventiveness, with huge lintels. Many of them have fallen, but here in the centre of the circle you can easily envisage its completeness.

The brute physical achievement is matched by remarkable sophistication about the workings of the cosmos. The stones appear to have been aligned so that at dawn on the summer solstice, the sun rises directly in the line from the "heel stone", set beyond the circle close to the road, and the altar stone.

"It's my favourite tour," says Jason, who conducts a wide range of trips. "Everyone has planned their visit months in advance, and is psyched up for something they have waited their whole lives to see."

The noise from the traffic seems to evaporate with the dew, with the silence broken only by the staccato of shutters. You feel strangely awed, reverential even, at being in the heart of such a profoundly mystical monument. Some places in Mayan Mexico and Guatemala feel like this, but they are tougher to reach, and much younger.

Time to take in the detail: the lichen in the tones of autumn that clings to the stone, bestowing texture and colour on sandstone worn pale by the elements. Early tourists painstakingly and shamefully carved their initials on one of the tallest stones, which – just below the waist-high messages – also bears ancient carvings of axe-heads.

The smaller slabs of bluestone within the circle are remarkable more for their provenance than their scale: the Preseli Hills in Wales, about 200 miles away – or, possibly, brought closer by glaciers. The more we know about Stonehenge, the more there is to know.

"It's exactly as I thought it would be," said David Gray from Manitoba in Canada, as we reluctantly walked back to the 21st century. Is that that a good thing, I wondered?

"Yes, it's a very good thing," he replied.

Travel essentials: Stonehenge

Opening times Stonehenge opens every day of the year except 24 and 25 December. Admission is £6.60. The basic opening times, from 16 October to 15 March, are 9.30am-4pm.

However, between now and 15 October and from16 March to the end of May, it opens 9.30am-6pm. FromJune to August it opens 9am-7pm.Access to the stones is in sessions before and, in summer, after these opening times. There are no visits in November (mainly to protect the ground due to likely weather conditions), but there are morning visits 1-18 December, throughout January (except New Year’s Day) and February, and then both morning and evening visits from March onwards.

More information

For details contact the Stone Circle Access Booking Office: 01722 34 38 34; englishheritage.org.uk/stonehenge .