A pyramid with a spaceship runway and a skyscraper-sized finger with an observation deck inside its painted blue nail are just some of the madcap — and forward-thinking — designs on display at a new exhibition featuring past dreamings of Melbourne.

A History of the Future: Imagining Melbourne displays designs, sculptures and planning ideas proposed by artists to city planners over the past 180 years.

A design entered into a Melbourne Landmarks competition in 1978, by American K Baumeister. ( K. Baumeister; Supplied: City Gallery )

The exhibition features panoramics of the city, underground roads to solve the city's traffic congestion woes — in 1918 — and a number of creative entries into the a 1978 landmark design competition.

"In recent years, Melbourne has been transformed, not by towering landmarks, dramatic demolitions or elevated walkways, but by subtle adjustments to the fine grain of its urban fabric," curator Clare Williamson said.

Lawn at Dawn, pre-dawn view of Swanston Street with grass laid for Victoria's sesquicentenary celebrations. By Robert Suggett, 1985. ( Supplied: City Gallery )

"Consider this: we may have ended up with an ornamental lake with islands in the shape of the British Isles, outdoor escalators across the face of the Melbourne Town Hall ... runways for short-take-off-and-landing aircraft in place of Birrarung Marr."

A History of the Future runs until August 12 at Melbourne Town Hall's City Gallery.