The skyscrapers and monuments steal the show above ground in the Big Apple. But below New York's iconic cityscape, another equally impressive world exists.

The city authorities are currently undertaking a $17 billion project to create the Second Avenue Subway - the first subway line completed under the city in over 80 years.

The 8 mile line which has been worked on intermittently since the 1920s is set to go from Manhattan's Hanover Square to Harlem's 125th street.

And you cannot blame construction workers if they get distracted by the location known as 'The Line That Time Forgot'.

Photos: Metropolitan Transport Authority