Constructed in 1846, it is one of the oldest in the city. The focal space here has been argued to have existed since ancient times, later abandoned but revived when Athens became a city once more. It is one of Athen's most prominent squares and perhaps its most blighted, until its most recent facelift in 2020.
From the 19th Century to the 1950s, the area's layout more literally approached that of a square, framed by broad paths to the edges and centrally, and surrounded by neoclassical buildings.
From 1925 to 1930, the underground railway between Piraeus and Athens was built, requiring further re-design of the square. Thus, Omonoia became circular and marble bars were put at the entrances of the railway stations.
The square's focus also featured a shading arc of palm trees until the 1950s, and a central fountain until 2000, while almost a century ago; a ceremonial cannon once aligned in a ring.
Omonoia, including its trees, was later and to great criticism demolished, except for the fountain, to make room for the ever-increasing traffic. The area now formed a pentagon facing northwest and a greener hexagon to the northeast, with a central circle.
Road areas continued to encroach on the previous design in the shape of a circle totaling 4 lanes, with part of the former road nevertheless transformed into a larger open pedestrian space; but to great regret half the neoclassical buildings in the western and northern areas were removed, although some neoclassical structures remain in the northern part and within Athinas Street.
The square's traffic route from the 19th Century until 1998 once more fully circumvented the center with 6 streets (Stadiou Street, Athinas Street, Pireos Avenue, Agiou Konstantinou Street, 3rd September Street, Eleftherios Venizelos Street), of which 5 also functioned as entrances and exits.
The once circular square with the hexagonal fountain, hosted for some time the iconic gigantic glass sculpture of the "Dromea" (the "Runner") by Costas Varotsos that presently is located in the Square of Megalis tou Genous Scholis, across from the National Art Gallery and the former Hilton Hotel building.
Omonoia Square remained closed during the construction works of Athens Metro, to become squared and take on its present look. Of course, many decorative measures were taken, such as the restoration of the facade of surrounding buildings (the "Baggeio" and the National Bank are good examples) and the removal of billboards.
Trees were later replanted within Omonoia and encircled the fountain once again. When part of the square was shut down for renovation ahead of the Athens 2004 Summer Olympics, it was decided to eliminate traffic from the west and east sides once and for all, reducing it to the westbound lanes at the southern section and the eastbound lanes at the south leaving one route.
However, the square, as it was temporarily delivered – with neither any greenery nor the element of water – resulted in strong, and justified, reactions about its unattractive image. For this reason, the square was put into the hands of the Municipality of Athens during the Olympic Games of 2004 and thus was "dressed" in green with the addition of trees (mainly olive trees), grass, and flowers in wooden beds, which were removed after the Games.
One way or another, Omonoia remained the core of the city and should not have only been noted as a practical place of gathering, but also as an area that needed to reach the status of an aesthetically pleasing location. Its contentious and usually unattractive design changes have dogged its 175+ years of existence. So there was a condonable explanation for merrymaking as Omonoia finally got the makeover it deserved when its fountain once again soared water into the night sky.
Athens' redesigned Omonoia Square with its 30-meter-wide famous round fountain spouting water an impressive 20 meters high is bound to bring hope and a much-needed sense of wonder to this part of the city that had endured the brunt of neglect over the past 2 decades. The Athens Municipality's "Shock and Awe" project with a total of 188 water jets and 177 underwater lights was received with discernible joyfulness by its citizens in May 2020.