The students in Ethnoarchaeology of Cities have recently identified a number of "ruins" (although we did not at the outset define a ruin). Here are a few of their photographs.
This "ruin" at 96th St and Amsterdam represents the conversion of an elegant structure (bank?) to a pharmacy.
This is an exposed pipe (water?, sewer?) on East 20th St.
And this is a building with the upper storeys blocked while the ground floor is still in use on 125th St.
And here is a ?fountain for horses or a washbasin? at 155th
This is another factory, but in Providence RI