From 1925 to 1930 the underground railway between Piraeus and Athens was built requiring further redesign of the Square. Omonoia Square became circular and marble bars are put at the entrances of the underground railway station. The Square started to resemble European prototypes and acquired an important commercial role. Due to the existence of the underground railway it was necessary to create also an underground ventilation system and in 1931 Mayor of Athens Spiros Merkouris suggested placing eight sculptures representing the mythological Muses to cover the openings of the ventilation vents. Although the problem was solved, the result did not satisfy Athenians’ aesthetic expectations and the statues were removed.