Created for developer British Land as part of its Broadgate estate, the DSDHA-designed park was suspended above train tracks between the station's Grade II-listed train shed and the Skidmore, Owings & Merrill-designed Exchange House, which also spans the tracks.
Named after the neighbouring Exchange House, DSDHA worked in collaboration with landscape architecture studio FFLO to add 14,000 plants with more than 140 species to the 1.5-acre square.
The studios aimed to create an accessible landscape that blends nature with its busy urban location. The square is now one of the City of London's largest green public squares.
The creation of the 420-square-metre green space has quadrupled the amount of planting in Broadgate and enhanced biodiversity, which the developer believes will enhance productivity of those working in the surrounding offices.
"Creating opportunities for people to encounter nature as part of their daily lives boosts wellbeing and productivity," said Matthew Webster, head of environmental at British Land.
"This new, green space has been designed to enhance both physical and mental health in a variety of ways – through providing an area for tranquillity, opportunities for social interaction, or through encouraging and making it easy for people to visit and move through the space."
DSDHA and FFLO aimed to create a space that could be used for both work – as an overflow for the surrounding offices – and recreation.
Its meandering pathways and cascading waterfall were built alondside numerous curved benches and grouping of chairs to be used for open-air working.
"Our ambition for this new park was to create a landscape that nurtures both plants and people through retrofitting nature into the heart of the City, breaking down perceived barriers to the surrounding areas, and offering a space that provides opportunities for both recuperation and recreation," explained DSDHA's founding director Deborah Saunt.
An amphitheatre made from terrazzo stone is located in the centre of the square and provides addition space for seating and an area for temporary events.
Exchange Square, which is now open to the public, is one of four public spaces redesigned by DSDHA over the past seven years.
Other examples of public squares and spaces include a multi-level city park in Cyprus' capital designed by Zaha Hadid Architects, the Xuhui Runway Park by Sasaki and an undulating public square in Copenhagen that contains parking for 2,000 bikes by COBE.
The photography is by Daniel Fisher.