More than 3,500 unusual and historical buildings across England will open their doors from September 11, giving the public the opportunity to look around some exciting heritage sites that are usually closed.

Dozens of Dorset venues will join in as part of the English Heritage project, which has taken over the reins from the Civic Trust. However, the East Dorset Heritage Trust (EDHT) believes the weekend of Heritage Open Days isn’t enough, so have extended the event in its area.

“To do the county justice we needed much longer, so we said let’s take the whole of next week,” explains Alan Wilson, director of EDHT.

“We have called it Dorset Architectural Heritage Week. It incorporates the national event but goes on until Sunday September 20.”

It is estimated that 90 per cent of people living in England live within 30 minutes of an English Heritage attraction and for the next ten days Dorset and Hampshire residents and visitors will get the chance to enjoy them for free.

“This is a great opportunity for people to explore the heritage on their doorsteps and see behind the scenes of some amazing buildings and hear the stories they have to tell,” says English Heritage regional director for the south west, Andrew Vines.

“The south west has a rich cultural heritage and I would like to thank all those organisations and individuals who are taking part this year.”

Among the Dorset attractions taking part are the Russell-Cotes Art Gallery and Museum and St Stephen’s and St Clement’s churches in Bournemouth, while in Poole there will be a tour of the Old Town and a chance to discover medieval treasures of the town.

Purbeck boasts a big selection of free open days, with Corfe Castle, the Clavell Tower at Kimmeridge and Lulworth Castle all involved.

In Wimborne, Kingston Lacy will be open, as will the Priest’s House Museum, and in Ringwood Moors Valley Country Park is taking part.

Last year, Heritage Open Days drew on the support of an army of 41,000 volunteers across the country, who opened up their buildings, gave tours and talks and organised activities and events.

“Heritage Open Days are thrilling,” says Baroness Andrews, chairman of English Heritage.

“They are an opportunity to explore places which, however familiar, are normally closed and therefore mysterious.”

A full directory of national events is available at www.heritageopendays.org.uk, and free local attractions are listed on www.visit edht.org.uk. Alternatively call 01202 888992 for more information.

The pick of the bunch - Alan Wilson picks his top five not-to-be-missed sites in Dorset.

1 Castleton water wheel, Sherborne “It pumped clean water into Sherborne until as late as 1959. It’s fully restored in perfect working order and it’s absolutely fascinating to see.”

Open: Sunday September 13 2 Blandford water tower “It used to be part of Blandford station and is now owned by Blandford Camera Club. There will be a presentation, they have got some lovely slides and pictures that they are going to show.”

Open: Wednesday September 16, 7pm 3 Historic guided tour of Christchurch “This is a lovely guided tour organised by the local History Society. They know the area exceptionally well and are very good at sharing their local knowledge.”

Starts: Wednesday September 16, 2pm.

4 Shillingstone Railway “Fantastic reconstruction and restoration work is taking place there. The station is lovely, really beautiful.”

Open: Sat, Sun, Wed, Sat, Sun, 10-4pm.

5 Allendale House, Wimborne “This is where the EDHT are based and I will be doing a talk there called “the story of rotten luck.” It’s an extraordinary story of the perils and pleasures of owning a listed building.”