Thousands of people walk along 125th Street between Park and Lexington Avenues each day and most do not linger. Commuters race to catch trains to Westchester, climbing up to the elevated Metro-North tracks. Others hurry down to the subway, bound for Midtown Manhattan or the Bronx.

They pass through a scene that conjures up all the worst stereotypes of urban disorder: closed storefronts, litter, public drug use, people nodding out. But on a deeper look, the block also reveals an ecosystem filled not just with despair, but fortitude and empathy, too.

Drug dealers. Drug users. Teachers. Doctors. Counselors. Police officers.

Some come to the block for help; others to help them. Some prey on the vulnerable. Others are just trying to make a few bucks and survive. Some have come to accept people addicted to drugs as part of their community; others wish the block was cleaner, safer — and would make them disappear if they could.

Every borough in the city has a place like this one, where urban woes seem to cluster. In the Bronx, it’s the commercial hub around 149th and Third Avenue. In Queens, parts of Jackson Heights.

But the scene around 125th draws particular attention because it is on a major commuter corridor and in the center of rapidly gentrifying Harlem.