North of Union Square and east of Chelsea, Flatiron is a kind of non-neighborhood that's at the center of everything. The name comes from the area's most prominent landmark, the Flatiron building, the triangular 22-story building at the intersection of Broadway, Fifth Avenue and 23rd Street.

For decades, housing options have been limited in this small area; the most popular type of residences were lofts. But recent years saw a dawning of a new era in Flatiron. Most notably, the neighborhood's once derelict patch of greenery, the 6.2-acre Madison Square Park, has received a makeover. Today, the park is well-manicured and attracts hordes of patient foodies to Danny Meyer's fast-food al-fresco joint, the Shake Shack.

Numerous residential buildings have sprouted around the park. Some have been conversions of office spaces, such as 141 Fifth Ave., 15 Madison Square North and the Grand Madison (225 Fifth Ave.), a 171-unit condo that sold at an average of $1,300 a square foot.

Then there's the new construction in Flatiron: Units at 60-story new development One Madison Park -- where Liev Schreiber and Naomi Watts bought a pad -- are seeing upwards of $2,000 a square foot for park views. And there's more luxury to come including One Madison Ave. designed by Daniel Libeskind and developed by Elad Properties, the company behind the conversion of the Plaza.