Dar Group, EPR Architects, Gpad London and Nicholas Hare Architects all came top in the contest, which called for an "iconic gateway" at the east London junction dubbed Silicon Roundabout, due to the high volume of tech companies in the area.
Gpad London has proposed creating a digital garden that will include a "forest of lights that generate electricity", while Nicholas Hare Architects wants to create a park that will "harnesses the social, environmental and economic aspirations of the area."
The competition was organised by Islington Council in partnership with the Mayor of London, Transport for London (TfL) and Hackney Council. It asked designers to consider how the street could look after the roundabout is removed, in 2019.
According to the organisers, they were selected because they were iconic, and because they prioritised pedestrians and cyclists to create inclusive spaces.
These four proposals will inform future plans for the public space. A formal procurement process will now begin to finalise the design, with a budget of £1 million allocated by Islington Council to realise the project.
"A separate, formal tender process will take place next to develop feasible, affordable designs for the iconic gateway to complement the wider transformation works," said a statement from Islington Council.
Claudia Webbe, Islington Council's executive member for environment and transport, who chaired the judging said: "Old Street is an iconic place, known across the world as a vibrant hub of technology and culture, and it inspired many bold and exciting design ideas for our open call."
"In an extremely competitive field, the judging panel has selected the entries that we believe offer the best ideas to create an iconic gateway for Old Street with a much improved environment for local people, cyclists and commuters, alongside the wider transformation of Old Street," she continued.
The competition was run as part of the council's and TfL's wider plans to reorganise the road interchange at Old Street. The 1960s roundabout will be entirely removed and a two-way traffic system will be reintroduced, creating a new public space.
Plans to remove the roundabout at Old Street come as several schemes to create pedestrianised zones are being considered in London.
Oxford Street is set to become a pedestrian-priority area by the end of the year, while Zaha Hadid Architects proposed a pedestrianised system for the whole city.