Broadway forms a dividing line between Chelsea to the west and the area that comprises Union Square and Gramercy Park . It is here, between the great avenues - Third, Park and Fifth - that midtown Manhattan's skyscrapers begin to rise from the low-lying buildings. Before heading on to those jaw-droppers, like the Empire State Building, it's certainly worth at least a jaunt around the more genteel parts of these two neighborhoods, which offer some decent architecture themselves, like the Flatiron Building . The #N, #R, #Q, #L, #W, #4, #5 and #6 trains all stop at Union Square.