Norwich is going to be invaded by historians in the next few days for this year’s Heritage Open Days. As PETER SARGENT discovers, it’s an event that can involve us all – especially for Norfolk’s Big Weekend.

Someone once wrote that the past is a foreign country - but that could not be further from the truth. Our history is all around us, under our feet, over our heads, sometimes behind the door of the house next door, occasionally in the snug of your local pub.

The trick is finding it. For the third successive year the hidden history of Norwich is being opened up to thousands of visitors. A four-day event beginning on Thursday, September 6, is expected to set new records for the number of properties opened and for the number of visitors.

This year's Heritage Open Days sees nearly 170 places signed up. Many will be familiar, such as Norwich Castle Museum, others less so. Organisers Norwich Heritage Economic and Regeneration Trust (HEART) say the idea is to open up places to the public that are not usually accessible, and encourage people to take a closer look at more familiar places.

Locations include grand and sometimes forgotten houses, churches and other places of worship, pubs and shops, Norwich City's Carrow Road football ground, a scientific research centre, an archaeology centre and a significant botanical display.

Sophie Cabot, engagement manager for Norwich HEART, hopes to exceed the 100,000 visits that took place in last year's Open Days.

“Primarily the event is aimed at people living in Norwich, but there is a mix of people, including friends and family who come specially to visit over the four days,” she said.

At least one visitor is travelling from Australia for the festival.

Although the event is taking place across the country, Norwich has the highest number of open places.

It is a charity specialising in heritage-led regeneration in Norwich which aims to co-ordinate management, conservation, education and promotion.

Themes this year include Norwich's role in the abolition of the slave trade in 1807. Sites such as St Andrew's Hall and the Friends Meeting House in Upper Goat Lane were involved in the long-running campaign that culminated in an Act of Parliament 200 years ago.

The city's part in botanical search is also commemorated (see panel).

Most of the sites are inside the city centre, within the old city walls, though there are some further afield. They include some of the many cellars and undercrofts dating from medieval times. Here is evidence that each generation builds upon the foundations laid by their ancestors.

Indulge, the restaurant and bar in Queen Street, features a 19th century building - and a sturdy vaulted medieval undercroft. Normally open only to private parties, the public can take a look down below.

Similarly Take Five in Tombland, the bar formerly known as the Louis Marchesi, features a 17th century building with another medieval cellar. Many other buildings in Tombland and the older parts of Norwich have the same, dating from a time when merchants needed large underground spaces to store goods.

Bedfords Bar and Restaurant in Old Post Office Yard, is a Grade II listed building that houses a scheduled ancient monument - its vault dates from the 13th century.

A number of churches - both in and out of use - are opening up their doors. It used to be said there was a church in Norwich for every week of the year (and a pub for every day!). Certainly the city has a long ecclesiastical pedigree.

Most of us who walk along bustling Queen Street each day probably pass the little church of St Mary the Less without noticing it. Tucked away between estate agents' offices and bars, this tiny building dates from the 13th century. In the 16th century textile workers moved to Norfolk from the Netherlands, creating an industry that helped make the city prosperous, and cemented links with the Low Countries. Known as the 'Strangers', they settled in large numbers, creating their own communities. St Mary the Less became a Flemish cloth hall, and was later known as the Walloon Church until the mid-19th century. It will be hosting an exhibition on 'Strangers in the Fens'.

Other places of worship to open up include Norwich Cathedral and St John's Roman Catholic Cathedral, which is hosting tours and exhibitions.

Many of these fine old buildings are in the care of the Historic Churches Trust, which seeks to preserve them. They include St Etheldreda's Church in King Street, now an artists' studio, St Clement's, probably the oldest in the city, believed to have been founded by Danish settlers in the 11th century.

Norfolk's tradition of religious dissent is embodied in the Octagon Unitarian Chapel and Old Meeting House (both in Colgate). The influential non-conformist Gurney family - founders of Barclays Bank - is remembered in a special walk of sites in central Norwich connected with them. Earlham Hall, the Gurney home near the modern UEA, where prison reformer Elizabeth Fry grew up, is also open.

Norwich wouldn't be Norwich without its pubs. Fittingly, a fair few are taking part in the open days, featuring exhibitions on local history. They include Delaneys, in St Andrew's Street, now an Irish bar; The Gardeners Arms/Murderers in Timberhill, site of a notorious 1895 murder when a man killed his wife; The Hog in Armour, near the site of the old Duke's Palace; The Ribs of Beef by the river on Wensum Street, and acclaimed Norwich School artist John Crome's local, The Woolpack in Muspole Street.

Not all hostelries survived. The Norwich Society is running a walking tour of 'lost pub' exteriors on Friday afternoon (subject to numbers).

A number of city shops are featuring displays highlighting Norwich heritage. Waterstone's book shop, in architect George Skipper's Art Deco masterpiece The Royal Arcade, is hosting a backroom tour. Other shops to visit include The Bear Shop in Elm Hill, which is opening up its secret garden, Beaujangles in Lower Goat Lane, which has a pointed barrel vault under the main shop floor and a number of shops in streets such as St Benedicts, Bedford Street and Bridewell Alley, all with exhibitions.

Norwich used to be known as the city of gardens. Although many have been gobbled up for housing, some gems remain. The 'hidden' Plantation Garden, next to the Catholic cathedral, is a fine example and has been lovingly restored, while the Bishop of Norwich's garden in the cathedral grounds is worth seeing.

There's much more. Football fans can tour Norwich City's Carrow Road ground, the Archive Centre at County Hall will help you trace the lineage of your house, the BBC is hosting a local history event at The Forum and the RAF Air Defence Radar Museum at RAF Coltishall is a newcomer for 2007.

t Some of the events featured need pre-booking, though places may still be available on a first-come-first-served basis by going to the Tourist Information Centre in The Forum. More information can be found in the brochure published recently in the EDP or at www.heritagecity.orgs/hods. Norwich HEART is based at The Guildhall. Tel 01603 305575. Website: www.heritagecity.org