[fernmyth]

You’ve hit on three of the four of Jane Jacobs’s conditions for a healthy, high-density neighborhood in her book “The Death and Life of Great American Cities”!

- Variety of building age/quality, to have rent levels that allow diversity of activities (low rent hole-in-the-wall for an art club; high rent, new construction, ground floor retail for luxury shopping)

- Variety of building use schedules to ensure eyes on the street at all hours and full utilization of infrastructure (including restaurants). A pure residential area or pure office park will fail this and turn into a ghost town at some hours. Hudson Yards might hit 2 schedules but not 3, which is the ideal.

- “a dozen dozen places in a five minute walk” allows niche businesses to survive, since the large effective service radius includes enough people to find some customers. Rockefeller Center’s arcade is actually quite important and covered in the book, since it cuts some too-long blocks into short enough blocks.

I don’t remember the fourth condition, so read the book to find out.

[_8j50]

Perhaps instead of buildings we can think "floors"?

[fennecfoxen]

I suspect that if the developer/landlord is out to capture all the value possible (as he is directly incentivized to do) having multiple floors just isn't going to be nearly enough.