A poem compresses much in a small space and adds music, thus heightening its meaning. The city is like poetry; it compresses all life, all races, and breeds, into a small island and adds music and the accompaniment of internal engines. The island of Manhattan is without any doubts the greatest human concentrate on earth

Question: greatest in what sense? The degree of concentration -concentrate- is greatest, or the concentrate as a city is greatest, like we say New York is the greatest city? Thanks.