Nowhere grants a clearer vision of how medieval Britain cared for the elderly and infirm, and among the country's scattering of other contemporary medical buildings none still serves its original essential purpose.

And this explains why managing the Great Hospital in Norwich is such a delicate balancing act, one that its current master, Air Commodore Kevin Pellatt, is trying to perform without upsetting anyone.

'We are part of the Heritage Open Days scheme,' he says. 'We have guided tours that we take around that we charge for, and we want to do more of that sort of thing. But we can't have people pitching up and wandering around. The Great Hospital is about the care of elderly people. We do want to share these magnificent buildings with people but we are not really a tourist attraction.'

From tomorrow the Great Hospital begins a new phase in the way it handles visitors by opening an interactive display area that delves into its 762 years of history.

Housed in the lodge in St Helen's Square, accessible by entering the hospital site from Bishopsgate, the small history room will open every Friday between 10am and midday. Visitors can peruse information boards, see a striking new aerial photograph of the grounds taken from the cathedral spire and select from a variety of films that combine archive footage and new interviews with residents and historians.

'It's very easy to talk about the hospital in terms of architecture,' said Air Commodore Pellatt, 'but we wanted to show it from a people's perspective so we have looked at it through the eyes of people through time.'

As you step inside you hear, playing quietly in the background, a recording of 17th century Italian composer Gregorio Allegri's Miserere, which sets Psalm 51 to music. It is the psalm that Walter de Suffield, bishop of Norwich and founder of the hospital in 1249, decreed should be sung by priests every day to save his soul. Two especially appropriate lines are also inscribed on a wall:

'Purge me with hyssop, and I shall be clean

Wash me, and I shall be whiter than snow.'

At the outset the Great Hospital's purpose was to ease its residents' suffering and give them the best possible chance of heading to Heaven rather than Hell. Chronic illness was endemic and life expectancy short. In the words of Carole Rawcliffe, professor of medieval history at the University of East Anglia who officially opened the refurbished Lodge last month, the medieval residents 'needed good food, rest, care and security, and that was what the hospital aimed to offer. It didn't cure people in a modern sense'.

The men who lived there – and they were all men, up to 30 at a time – attended several church services each day, confessed their sins and received the last rites on their death beds.

Now the 10-acre complex in the heart of the city houses a population of elderly men and women. One of them, Joan Smith, describes on film how 'it seems like years and years of tradition, love and care have left their mark' there. But it is also home to a wealth of historic relics unknown to many people who are familiar with the riches of the nearby Anglican cathedral.

Most people know the cathedral's cloisters but not so many are aware that another perfect medieval quadrant lies a couple of hundred metres north-east. Many have peered upwards to squint at the cathedral's roof bosses, but relatively few know the similarly ornate ones in the transept of St Helen's Church – nor the more striking sight to be found in its chancel. Emblazoned with 252 black eagles painted to mark Anne of Bohemia's visit in 1383, its medieval ceiling is one of the finest in Europe. During the Reformation the chancel was reconstructed to include an upper floor, which later became home to the hospital's female residents. This ceiling gives the Eagle Ward its name, and while that element is an amazing medieval survival, stepping inside is otherwise like walking into a time capsule from the mid-20th century. After its last residents left in the early 1980s the ward was frozen in time, and visitors today can see some of the clothes, books and furniture owned by people who spent their final years there. Like the rest of the Great Hospital grounds, it has a rare feeling of stillness, despite the bustling city centre.

Administrator Maureen Eastman, who has worked there for 20 years, said: 'It's right in the middle of Norwich but you can walk around here some days and not hear a thing'.

The Great Hospital site's significance is such that last year its archive was listed on the Unesco UK Memory of the World Register, an online catalogue that promotes the country's most important historic documents – visit the website at www.unesco.org.uk/ukregister for more details. At the time David Dawson, chairman of the UK Memory of the World Committee, said: 'These are some of the UK's exceptional, but lesser-known documentary riches. By awarding them with the globally-recognised Unesco Memory of the World status we hope to elevate them to the world stage.'

The Unesco citation states: 'The medieval records of St Giles's Hospital at Norwich (known the 'Great Hospital')... have no rival anywhere in the country. They are the fullest and by far the most important set of British medieval hospital records to survive the English Reformation.

'There were over 1,300 hospitals in medieval England, almost all of which were destroyed, with their records, at the Reformation. The Great Hospital was one of very few which survived.'

It almost didn't, however – when Henry VIII died in 1547 the hospital passed to the new Protestant monarch Edward VI, making its future uncertain. But the Norwich corporation petitioned for the hospital to survive in order that it might help care for the growing number of poor people in the city, and the king relented and returned the ownership of the hospital to the corporation.

Now the archive held at Norfolk Record Office, which features in one of the new short films at the lodge, gives an unrivalled view of how hospitals worked in the medieval period. Although all the residents were male, there was a female presence in the form of four female nurses, who according to Prof Rawcliffe 'had to be over 50 so that they didn't offer any temptation to the patients!'

There was a slaughterhouse, a swan pit, a bakery and an orchard. The site sits in a bend on the River Wensum, and there was a quay so that fish could be ferried up the river from Great Yarmouth.

'The diet was boring but nutritious,' says Prof Rawcliffe. 'It was high in Omega 3, which doctors today tell us we should be eating. So we shouldn't be too disparaging about the diet.'

The records reveal the management of the daily supplies of food and drink, the hospital's portfolio of other estates and properties, and the donations received by patrons. The lodge's refurbishment was achieved thanks to a bequest in 2010 by Colin Jury, one of the latest in a centuries-long line of generous donors to the Great Hospital.

For although the site remains relatively unknown to many people in Norfolk, to those who have a connection it is a cherished place. The hope now is that by careful management it will start to connect with a wider audience of people keen to discover another aspect of Norwich's incredible breadth of heritage.

'We do want to open it up, but we have to do it very carefully,' says Air Commodore Pellatt. 'We have to acknowledge the fact that people are living here – there's a very fine dividing line between making it accessible and intruding into people's lives.'

For more information about the Great Hospital as a care home visit the website at www.greathospital.org.uk. For more details of its historic importance visit www.thegreathospital.co.uk

Tours can be booked for �75 for 25 people – telephone Maureen Eastman on 01603 622022 or e-mail maureen@greathospital.org