PHOTOS: See the new artworks set to reshape Sydney

A controversial new $3.5 million artwork that will alter Sydney's skyline is lighting up Twitter, drawing comparisons to everything from a roller coaster to a 'space noodle'.

Cloud Arch, by Japanese artist Junya Ishigami, is one of three new artworks approved by the City of Sydney for its $9.3 million city centre public art plan.

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Lord Mayor Clover Moore said the "momentous" arch would stand between 50m and 75m over George Street.

The Pavilion, a $2.5 million work by Hany Armanious designed to resemble an overturned milk crate, will provide a public gathering place near the city's Central railway station.

British artist Tracey Emin's $2.1 million proposal to create a corridor of bronze bird installations near Wynyard has also been approved by the council.

"The artworks ... will cement Sydney's reputation as a capital of culture and creativity", Ms Moore said.

However, Cloud Arch has already attracted criticism on Twitter for its design and cost.

Mr Ishigami said he wanted the artwork to become a new symbol of a "green, global and connected" city.

"The Cloud evokes comfort, openness and freedom," he said.

The city council will now begin a thorough design development process for all three works, including extensive consultation with local businesses and residents.

All works are expected to be installed from 2017, in line with the implementation of the CBD and south east light rail line.

Ms Moore said the plan was part of the council's $220 million contribution tot he NSW Government's light rail project, and aimed to transform the city with major public area upgrades.

The three installations are the latest of hundreds of artworks scattered throughout Sydney.

Artists have for years found a ready home for their work on the city's streets, with installations that provide a focus for local communities and entertainment for visitors and tourists.

See some of Sydney's current installations below