It comes as builders uncover historic gems hidden by years of neglect at the heritage CBD building, Pall Mall Nominees director Graham McMahon says.

"It's been a project four years in the making and we only really started serious work a bit over 12 months ago. Nothing seemed to be happening until the last month and its all started to come together," he said.

Discoveries so far have included previously boxed-in metal columns, hidden plaster arches and a steel strongroom door thought to have once blocked the public from gold stored on the premises.

"Our builders, from DBG properties, have taken real ownership of the project. Every time they find something they are on the phone to us and sending photos," Mr McMahon said.

June 2018: Beehive Building works begin | Photos

Visitors to the Beehive during Open House Weekend will be able to see the upper story shops and walkway for the first time, he said.

The event's program includes 26 other buildings as well as walking tours, film screenings and talks - all aimed at shining a light on spaces of architectural excellence.

A full program is now available online at openhousebendigo.org and will be in the Bendigo Advertiser on Saturday 12 October.

The event takes place on 26 and 27 October.

More: After huge success, Open House Bendigo to return for two more years

Open House visitors will be the first to see the beautifully restored 1872 Beehive Building (artist impression pictured right), which has been returned to its former glory after extensive works by Williams Boag Architects. Similar in style to Melbourne's Royal Arcade and by the same designer, Charles Webb, the building's original uses include a hotel, a mining exchange, a restaurant, offices and function space.

The current development uncovers the rich layers of use by removing most of, if not all of the 1920s' and 1950s' changes, revealing key features of the original building.

Visitors had access to the ground level construction site during the 2018 Open House Bendigo program, and this year visitors will access the newly completed arcade including the second story, revealing the intricate beauty of the glass ceiling not seen for decades.

With a sustainable focus and a restricted budget, Koorork House II (pictured left) - created by e+ architecture - exemplifies the architect's desire to create imaginative containers for living. A concept based on 'making camp' drove the conceptual design.

The central space where the family comes together around the fire is flanked by four rooms of flexible proportions, allowing for a series of different uses.

At only 160 square metres, Kooroork House II highlights how family homes on a budget are possible without compromising on sustainable and design aspirations.

One of the main drivers for the architect/owners in developing the site was the view to this being their 'forever' house, rather than a stepping stone to something bigger and 'better'.

Stage 1 involved the basic renovation of the interior, ensuring the 'bones' were in good health. More recently, Stage 2 has been completed.

This involved reconfiguration of internal spaces and a modest extension providing more living space, improved connection to the garden and improved natural light.

Responding to a brief to increase the living areas of the existing house and rationalise the rear lean-to extension, the new addition does not dominate the streetscape, whilst still being clear that it is contemporary in its design and build.

Working within the heritage overlay, Short Street (pictured right) uses 'traditional' materials such as zinc and hardwoods, with crafted elements such as the windows, doors and joinery to 'tip its hat' to the past era features, now restored to former condition.

Originally constructed for no more than £260, this heritage listed lock-up (pictured left) was in use up until 1963.

It will open its doors to the public on Saturday 26 October, when the public can experience the sensation of being locked in the logs, with the heavy doors closed behind them.

The walls and floor are made up entirely of locally sourced, rough-hewn logs and, due to pristine maintenance over the years, the lock-up is one of only five remaining in the state.

Filled with a number of artefacts from the Goldfields era, the lock-up presents a fascinating window into Victoria's criminal past.

The symbolic heart of the Eaglehawk community - a remarkable investment for a borough consisting predominantly of poor mining families.

It is now home to the Star Cinema, a not-for-profit community organisation offering a boutique cinema experience, providing current releases as well as weekly classics for the local community.

Hear from local architect Katrina Logan, with guided tours across two residential projects including:

First established in 1895, Thompson's Foundry (pictured right) operated under the Thompson's name for over 100 years.

A significant manufacturing hub, the foundry produced a wide variety of industrial equipment, including steam engines, mining equipment and sluicing and dredging equipment.

The site is still in active use, with Open House Bendigo providing a rare chance for visitors to see inside this significant industrial landmark.

All residential homes and Castlemaine buildings are pre-booked, with bookings opening Monday 14 October at 8.30am.