Topography is minimal, roads are off-scale wide, towns are indicated by symbolic walls or towers — more of a traveler's guide but much too large to serve as a handy road map.
The 23-foot-wide town house at 11 East 67th was built in 1881.
The 25-foot-wide town houses, dating to 1856, are among the oldest buildings on the avenue.
Next door, Ms. Chiang is listing another 20-foot-wide town house for sale, this time for $13.5 million.
Ms. Hunter's two-bedroom apartment, in a 27-foot-wide town house co-op, was listed at $3.2 million.
The 20-foot-wide town house has seven bedrooms, five bathrooms, two half baths, a chef's kitchen, a formal dining room, a parlor and four working fireplaces.
In 2005, Mr. Quinlan paid $26.25 million for the 25-foot-wide town house, at 20 East 64th Street between Fifth and Madison, property records show.
The 25-foot-wide town house has four bedrooms, four and a half baths and 1,700 square feet of outdoor space divided among terraces and a garden.
Last year, a 20-foot-wide town house at 67 Charles Street, just off Bleecker Street in the West Village, was listed for nearly $13 million.
In 1911 Clark began a 50-foot-wide town house at 46 East 70th Street, in a center of mansion-building activity.
