Cromford Mill, site of Richard Arkwright's technological advances. © Crown copyright

Heritage Open Days 2007 is running from September 6-9, with historic and unusual buildings across England that are not normally open to the public, or that charge admission, throwing their doors open for free.

Established in 1994 as England’s contribution to European Heritage Days, this annual event attracted more than 1 million visitors last year with hundreds of venues taking part manned by thousands of volunteers sharing their knowledge and expertise, making it the country’s largest voluntary cultural event.

Organised by the Civic Trust and English Heritage, it aims to celebrate England’s architecture and culture. As well as opening up unusual buildings, Heritage Open Days also includes tours, activities and many other events exploring local architecture and culture.

Chester Roman Amphitheatre will be hosting gladitorial displays and a changing of the Roman guard. Photo Chester Archaeology

“Heritage Open Days this year is set to be even bigger than last year, so even if you are a regular Heritage Open Days-goer there will be something new for you to see and do,” said Dr Simon Thurley, Chief Executive, English Heritage.

“This is a chance to explore not just country houses but the history and culture of everything from Buddhist temples and Masonic lodges to mines, farms, pubs and factories.”

As the weekend approaches we have picked out just some of the most unusual and interesting places that will be revealing their hidden treasures.

Landrover tours are leaving from Brighton’s Royal Pavilion on Saturday, heading up onto the South Downs to discover the ‘Chattri’, a monument built on the cremation site of Hindu and Sikh soldiers who were hospitalised in Brighton after fighting for Britain in the First World War.

Manchester's Victoria Baths will be open for visitors to view the restoration work. Photo Creative Commons Sharealive2.5 licence

The first purpose built mosque in Britain isn’t in one of England’s big urban centres like London or Birmingham, but in suburban Woking. The Shah Jehan Mosque, built in 1889, is opening its doors on Saturday and Sunday, where visitors can join a tour and discover the building’s traditional Islamic design with decorative tiles and Arabic calligraphy.

Sir Richard Arkwright was one of the driving forces behind Britain’s industrialisation, and Cromford Mill in Matlock, Derbyshire, was where he established the world’s first successful water-powered cotton spinning mill. The mill is part of the Derwent Valley Mills World Heritage Site and Arkwright Society guides will lead tours of the site throughout Heritage Open Days.

Chester is well known for its walls and Tudor buildings, but not everyone is aware that it is also home to the remains of one of the biggest Roman amphitheatres in the country. It is still being excavated with new discoveries being made all the time, and there will be an exhibition there plus, on the Sunday, a special display of gladiatorial combat and changing of the Roman guard.

Heritage Open Days sees a rare opportunity to step inside one of York’s most well kept secrets – the ancient Church of St Martin-cum-Gregory in Micklegate. The church is soon to become a national centre for exploring the world of stained glass and is packed full of glittering treasures.

Dragon Hall is the starting point for a tour of historic King Street. Photo: Jayna Makwana © 24 Hour Museum

Over in Manchester the Victoria Baths, winners of BBC TV’s Restoration programme in 2003, will be opening all weekend, with access to the three pool halls and viewing points of the restoration site. Guided tours will show the boiler house, water treatment rooms and the undercroft of the pools and there will be hands-on workshops in stained glass and tile making.

Since it inception, every region of England has taken the Heritage Open Days concept to its heart – but special mention must be made of Norwich, which has some 170 venues opening over the four days, from guided tours of the archives and records centre to glimpses of the city’s many medieval undercrofts.

They’ve even set up their own website so you can see all that the city has to offer.

London also organises its own heritage days, but on a different weekend in September, with Open House London, while Scotland runs Doors Open Days and Wales and Northern Ireland also run their own European Heritage Days. For details of these other events go to the Heritage Days website.