The new stretch of Sydney Metro line from Chatswood to Sydenham might just be the city's first Instagrammable public transport project.

Until now, the underground train stations of Sydney's CBD have been little more than grubby pit stops where swarms of harried office workers rush through with barely a passing thought.

But those behind the new metro project hope that its gleaming new stations, dotted with large architectural-scale artworks, will have commuters looking twice — and taking a moment to pause and reflect.

There's everything from revolving soundscapes and light installations to a giant mural featuring hundreds of Indigenous footprints or a floor mosaic that's a cross between an athletics track and a meditation walk.

Sydney Metro City and Southwest project director Hugh Lawson said the artworks breathe life into very large and otherwise highly functional spaces, which will fill with commuters when the rail line opens tomorrow morning.

"The art in particular does really lift the stations and bring them out of the ordinary into something extraordinary," he said.

How does it compare to metro art around the world?

Metro systems around the world have a long history of being a giant canvas for public art — and some of them are so beautiful they've become tourist destinations in their own right.

The stunning, swirling murals of the "cave" stations along Sweden's Stockholm Metro are often referred to as the world's longest art gallery.

Commuters at Naples' Toledo station can ride an escalator near a surreal blue-and-green seascape mural while staring up at light spilling through from the world above via a huge oval-shaped void called the Crater de Luz.

The Portuguese capital Lisbon has the Olaias station, which looks like Picasso has scrambled a Rubix cube.

And the grand yellow baroque ceiling, chandeliers and murals of Moscow's Komsomolskaya station are still jaw-dropping, more than 70 years after they were built as a tribute to Stalinism.

Even North Korea has got in on the act with its metro in Pyongyang.

What was the thinking behind the art on Sydney's metro line?

The artworks chosen for the Sydney Metro City line aren't just any pieces of art.

They had to have imposing scale to make an impact in the metro stations' cavernous spaces and be made of durable materials that could be easily cleaned of daily grime.

But Sydney Metro's associate director of design Kati Westlake said the artists also had to work around practical challenges, like how to incorporate non-negotiable features of stations like fire doors and signage.

"It is quite a tough job for artists, working on a big infrastructure project like this, simply because there's a lot of technical and functional things that they may not have to deal with on other art projects," she said.

"The sheer length of time and the sheer number of people involved really make it quite an extraordinary experience."

The artworks have also been carefully commissioned to give the stations a sense of place that's unique to their location and community.

There are recurring themes that connect commuters with Sydney's natural environment, its First Nations' heritage and culture, as well as materials and imagery that reference the city's colonial history.

"We're spending public money so we really want that art to be engaging and we want people to respond to it," Ms Westlake said.

"We want them to enjoy it, and really maximise the number of people who can come into contact with that art."

What are some of the things I will see using the new metro?

A 9.7-metre-high black-and-white portrait of a smiling seven-year-old Indigenous dancer named Roscoe greets commuters on the concourse of Waterloo station.

Meanwhile the escalator takes you on a journey past a sparkling mural sprinkled with hundreds of community members' footprints, stylised and cast in gold and silver.

The footprints, created by Indigenous artist Nicole Monk, form a map that symbolises stories and walking tracks of the local area.

The pedestrian tunnel linking the new Martin Place metro station with the existing heavy rail station has been called Mulu Giligu — meaning "path of light" in the Gadigal language.

It will play host to evolving immersive sound and lightscapes, like Tina Havelock Stevens' Sonic Luminescence, which plays recordings made in Martin Place and on metro train platforms, along with a "pre-colonial symphony" of magpies, butcherbirds and owls, interspersed with vocals and violins improvised by Indigenous musicians.

An algorithm ensures you'll never experience the work the same way twice.

Artist Callum Morton used 10,000 brightly coloured porcelain enamel tiles to create two soaring murals at both entrances to Gadigal station, near Town Hall.

The 13-metre-high bold curving images of train tunnels have a deliberately Looney Tunes feel but also make reference to the freshwater Tankstream that once ran nearby.

Ms Westlake says the style and choice of material is also a nod to other famous tiled artworks in underground stations around the world.

"[Mr Morton] has seen the incredible tileworks in the London Underground and the subway in New York and knows the history of those tileworks, so that is part of the reason I guess that he chose to create this work in tiles," she said.

People who've used Central station's already opened new North-South concourse will already be familiar with the giant 113x19-metre terrazzo floor drawing — which was built as part of Sydney Metro's transformation of the station.

The artwork looks like a giant athletics track guiding commuters as they rush to their destination — but take a second look and you'll notice the floor is inlaid with meditative phrases such as "simply breathe naturally" and "stay focused when everything moves around you".

The artwork by Rose Nolan is titled All Alongside of Each Other and it is one of the largest pieces of art to be installed inside any Australian railway station.