Professional walking tours in this city usually cost $30 to $50 and require booking a slot two weeks out. The Flatiron NoMad Partnership runs one that costs nothing and takes walk-ups — and it has been running long enough that the guides are genuine specialists rather than script-readers.

  • When: 11:00 a.m. on the first Sunday of every month, rain or shine. Next one: Sunday, October 4.
  • Where it meets: the tip of the Flatiron Building, on 23rd Street just east of 5th Avenue.
  • Cost and sign-up: free. No RSVP, no registration, no ticket — you just show up.
  • How long: about 90 minutes on foot through the Flatiron and NoMad districts, including Madison Square Park.
  • What you’ll see: the Flatiron Building, the New York Life Building, the MetLife Clock Tower and the Appellate Courthouse, plus the neighborhood’s architectural and social history — the Partnership’s own pitch is “fascinating details and even scandalous tidbits.”
  • If you’d rather go alone: the Partnership also publishes a free self-guided tour brochure you can download and follow on your own schedule.
  • The guides: Miriam Berman, an urban archivist and author of “Madison Square: The Park and Its Celebrated Landmarks”; Mike Kabak, a 20-year professional guide who has worked the Flatiron district for 15 of them; and Fred Cookinham, a historian who has led in-depth tours of the district since 2007 and written “Man in the Place of the Gods: What Cities Mean.”

The reason to care about who the guides are: this is the difference between a tour that recites construction dates and one that knows that Miriam Berman consulted on the Flatiron Building’s centennial exhibition for the New-York Historical Society, or that Fred Cookinham has taught the neighborhood to Columbia architecture students. That kind of knowledge normally comes attached to a fee.

It is also the rare free cultural programming that asks nothing of you — no lottery, no app, no reservation that can be cancelled out from under you. The trade-off is that the schedule is monthly rather than weekly, so the practical move is to put the first Sunday of each month on the calendar and treat the 11 a.m. meeting point as fixed.