BRISBANE'S City is extending an invitation to explore a range of architectural wonders which are being showcased at the sixth annual Brisbane Open House.

This year's Brisbane Open House offers an unprecedented opportunity to tour almost 100 places and spaces around greater Brisbane, including 30 buildings participating in the free event for the first time.

Access to a vast array of historic and contemporary buildings is offered to visitors who will relish the chance to unlock some of Brisbane's most intriguing places, with free talks by the city's architects and opportunities to tour marvels of design, including Archerfield Airport, the Brisbane General Post Office (GPO), UQ Oral Health building, Queensland Emergency Operations Centre, Brisbane City Council's Spring Hill Service Reservoirs, Roma Street Station Heritage Building, Fernberg (Government House) and Hobbs Park.

Princess Theatre at 8 Annerley Rd, Woolloongabba.

Ben Lyons, President of the Brisbane Development Association said this year's program offered an extraordinary line-up, with something for everyone.

"This year, Brisbane Open House's diverse program is sure to appeal to everyone," Mr Lyons said.

"We have a fascinating selection of influential presenters discussing insightful topics at our Speaker Series, which now runs for five weeks.

"Our Made in Brisbane program offers backstage passes to meet the makers, explore their studios and workshops and understand their creative processes, while our Children's Program will keep the kids entertained with fascinating free workshops and activities across the weekend."

Also on offer in 2015 is the ever-popular photo competition, guided walking tours of precincts and free concerts presented by Brisbane City Council's Bands in Parks Initiative and the Queensland Performing Arts Centre.

Brisbane Open House visitors will learn more about the participating buildings thanks to some of the city's most respected architects holding special guided tours.

Organisers are calling for volunteers to help with the guided tours.

Last year more than 500 locals donated their time to Brisbane Open House.

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