REMOVE

1. sky
2. barriers
3. rubbish
4. soil
5. mountains
6. scaffolds
7. fences

WHAT

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

More 

WHERE

1. New York, New York (1)

WHEN

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