What is it about a building we’re not allowed into that makes us desperate to see inside? For those with curiosity about Melbourne’s most interesting – and also most secret spaces – Open House Melbourne will be unlocking doors across the city on July 25 and 26.

Most of the 105 buildings on the bill will be accessible for self-guided tours. A small number of buildings will only be available for limited, pre-booked tours – unlike previous years, there will be no ballot system in 2015.

Building highlights for this year's Open House Weekend are many, but include the long-abandoned Argus Building, the modernist Cairo Flats in Fitzroy, the heritage-listed Meat Market in North Melbourne, the subterranean ‘J’ Substation, the new Library at the Dock, Northcote Hemp House, Melbourne School of Design, RMIT Design Hub. Also, a look inside the under-construction Victorian Comprehensive Cancer Centre, which is due for completion in 2016.

The ever-popular Flinders Street Station Ballroom will be unlocked again to a very select few – a total of 20 people. Broadsheet will be giving away three double passes next week – so stay tuned.

There will be a series of fascinating tours over the big weekend, including a Rooftops of Melbourne tour, a guided look inside the Sussan and Sportsgirl headquarters in Cremorne, and a historical insight into Luna Park in St Kilda.

Open House Melbourne has run annually since 2008 in an effort to include the public in the pursuit and understanding of good design within the city. Year after year, the Open House Weekend has proved to be hugely popular, attracting more than 130,000 visitors in 2014.

Beyond the Open House Weekend, there will also be a series of free design talks and walking tours all throughout July. Some events to look out for include local architect Peter Johnson speaking on the Lost St Kilda Mansions, and when Open House teams up with Nite Art for a special nocturnal art walk across the city.

For the full program, visit openhousemelbourne.org . Bookings open on Wednesday July 8 at 10am until booked out.