Sydney may be one of the world's most expensive cities to live in, but you can't complain that it doesn't do things for nada. While there's many paid events at Vivid Sydney this month, there's just as many spectacular and Instagrammable sights to be enjoyed for free.

Take, for example, the 60 plus light installations scheduled to run over the two-and-a-half-week schedule, which will literally set the city ablaze with colour. While some installations will be impossoble to miss on your commute home, others are worth leaving the comfort of your lounge room for. Here, we pick the seven Vivid Light installations you'd be crazy not to see.

Related story: Top ten: the insider's guide to the Vivid Sydney festival 

Lights, city, action! 7 things to see at Vivid that don’t cost a cent

1. Life Story, The Rocks

One for the Sir David Attenborough fan in all of us - this extra-special light installation at The Rocks' Argyle Cut features sights and sounds from BBC Earth's Life Story production. Narrated by the world's most recognisable doco voiceover (aka Attenborough), Life Story will be brought to, er, life as a spiralling vortex of birds, animals and sea creatures. Epic.  

Related story: 3 Sydney Film Festival documentaries you simply can't miss 

Lights, city, action! 7 things to see at Vivid that don’t cost a cent

2. Vivid Laser Fountain Water Theatre, Darling Harbour

Created by artist Oracle-Liquid (Glenn Turner) as a kind of liquid light show, this Darling Harbour installation is a crazy blend of lasers and jets of shooting water. With a centrepiece containing jets that shoot 100m across the harbour and 30m into the air, the presentation is a feat of technology and (thankfully) recycled water. Not just for the kiddies, be sure to listen out for three bespoke DJ sets created specially by The Presets, too.

Related story: Future Classic celebrate 10 years with Vivid Sydney concert 

3. Light Origami, Alfred St, Curcular Quay

A collaboration between Japanese artists Masakazu Shirane and Saya Miyazak and local talent Reuben Young, Light Origami poses itself as a giant 3D kaleidoscope constructed from over 1,100 origami shapes made out of Perspex. The changing  light spectrums projected within the space give users the uncanny experience of being inside a large-scale kaleidoscope.

Related story: Taking art to the streets: PUBLIC 2015 

Lights, city, action! 7 things to see at Vivid that don’t cost a cent

4. Vivid Light Walk

While this year's lighting of the Opera House sails comes courtesy of UK directive Universal Everything (founder Matt Pyke has worked with everyone from Radiohead to the London 2012 Olympics), a trip to see the sights is not complete without a walk along the forecourt. Starting with the Siamese fighting fish on the Opera House forecourt, walking towards East Circular Quay will introduce you to The Heart of the City, Light Origami and the Museum of Sydney's floating glass cube. Don't forget to journey to Campbell's Cove either - there you'll meet Dolly - a three-metre high crochet doll lit up like beacon, plus the Geometric Eye that watches over the city.

Related story: Radiohead designer Stanley Donwood exhibits at Carriageworks

Lights, city, action! 7 things to see at Vivid that don’t cost a cent

5. The Dresses, Kendall Lane, The Rocks

If you keep walking along the Vivid Light Walk, you'll find a ton of amazing sights at The Rocks. One not to miss is Tae Gon Kim's The Dresses, containing hundreds of fibre-optic cables which have been fashioned into three eerily glowing gowns. Inspired by a quote from French theorist Roland Barthes, the dresses propel the viewer to think about the nature of love and relationships. 

Related story: What to expect from Marina Abramovic's landmark Australian visit 

Lights, city, action! 7 things to see at Vivid that don’t cost a cent

6. Mechanised Colour Assemblage, Museum of Contemporary Art

We've mentioned artist Rebecca Baumann's involvement in Vivid before, but her transformation (alongside Paris-based design team Danny Rose) of the MCA façade from serious gallery to pulsating light installation is one of the festival's highlights. A listening and viewing experience like no other, the façade will feature a series of 'machines' that constantly change colour and shape. Don't miss it.

Related story: Dreaming in technicolour: Rebecca Baumann's vivid installations

Lights, city, action! 7 things to see at Vivid that don’t cost a cent

7. Flowing River of Light

One of Vivid Ideas Curator Jess Scully's top ten picks, Chatswood's underwater-themed installation will feature rippling light projections that serve to turn the Chatswood Interchange and Mall into a shimmering river complete with LED lit-trees and an ambient water soundtrack. It's the perfect excuse to leave the confines of the CBD for a night.

Related story: Bright sparks: the 8 most inspiring light artists