From Chapter 5 of The Death and Life of Great American Cities:

Cities are full of generalized parks that can hardly be expected

to justify themselves, even if their districts are successfully enlivened.

This is because some parks are basically unfitted, whether

by location, size or shape, to serve successfully in the publicyard

fashion I have been discussing. Nor are they fitted by size

or inherent variety of scene to become major metropolitan parks.

What can be done with them?

Some of these, if sufficiently small, can do another job well:

simply pleasing the eye. San Francisco is good at this. A tiny

triangular street intersection leftover, which in most cities would

either be flattened into asphalt or else have a hedge, a few benches

and be a dusty nonentity, in San Francisco is a fenced miniature

world of its own, a deep, cool world of water and exotic forest,

populated by the birds that have been attracted. You cannot go

in yourself. You do not need to, because your eyes go in and take

you farther into this world than feet could ever go.