REMOVE

1. plants
2. sky
3. stairs
4. bushes
5. railings (balustrades)
6. after 1966

WHAT

1. Visual Works (hierarchy n … (1)
2. arcades (structural assem … (1)
3. artists (visual artists) (1)
4. barriers (1)
5. benches (furniture) (1)

More 

WHERE

1. New York, New York (1)

WHEN

1. 1964 (1)
2. ca. 1964 (1)