Tree-lined Andrássy út, built during Hungary`s Golden Age, has deservedly been called the most beautiful street in the city. The commercial part of the street runs from Bajcsy-Zsilinszky út to Oktogon. Thereafter the boulevard becomes quieter and more picturesque. Traffic islands separate the sidewalks from the street, and stores give way to apartment houses, theatres and - near Hősök tere - a diplomatic quarter. Oktogon and Kodály kőrönd, the two main squares encountered along the way, are both striking uses of public space. Running just beneath the street surface is the M1: when it opened in 1896, it was the first metro line in continental Europe.