After a century and a half, the $40-million extension by Peter Elliott Architecture, Urban Design and TCL (Taylor Cullity Lethlean) has delivered a much-needed extension to Victoria’s historic Parliament House.

Victoria’s Parliament House, designed by architect Peter Kerr in the mid-19th century, was never fully realised.

The garden surrounding Victoria's Parliament House was first established in 1856, the same year that the parliament of the then-fledgling state of Victoria opened, it saw some early changes in style, but the enduring design is believed to be the work of William Guilfoyle – the designer of the Royal Botanic Gardens, Melbourne.

While the building’s Spring Street façade is the only elevation that remains true to the original grand vision.

Arranged to protect established trees, maintain valued views, and be subsumed within a grand landscape, the new pincer-shaped extension is largely sunken below ground with 100 percent of its footprint accommodating new accessible garden spaces, creating one of the largest green roofs in Melbourne’s CBD.

“The landscape design approach was to soften the edges of the new building and create a dynamic garden threshold between the new and the old,” explains TCL director Perry Lethlean.

According to Peter Elliott of Peter Elliott Architecture and Urban Design, the expression of the building façade adopts two distinct languages.

“One [of these languages] is a ramparted bluestone outer wall nestled into the existing gardens, the other a more formal grid of office windows wrapping the central courtyard,” said Elliott.

The 19th century garden has been complemented with heritage planting but also juxtaposed with more contemporary garden expressions such as a sunken courtyard that takes a cloistered form and provides a new social setting for parliamentarians and lets natural light flood into the new building.

This space references the existing garden, using its emblematic planting to create compositions of overlapping textures.

More than 12,000 plants frame a central sloping lawn and terrace that can be used for events and announcements.

The roof garden atop of the new building introduces an Australian meadow (designed with Paul Thompson) to emphatically place this contemporary building in its broader loci.

Structured via drifts of silver Eremophila nivea and Eremophila glabra, the roof garden features a serpentine bluestone path that weaves through a rich mosaic of native shrubs, grasses and wildflowers, providing a powerful new setting to the remarkable ensemble of 19th century buildings.

The new gardens have been designed to encourage greater biodiversity within the dense urban context, provide thermal insulation to the new building and create iconic spaces for events, announcements and contemplation.