*Valencia Street in San Francisco is for much of its length parallel to Mission Street, but then it says, "This is silly," and jogs over and dead-ends into Mission.

Parallel lines meeting here and now is an activity that fits San Francisco, which doesn't have one strong grid system, but various grid systems in different parts of town, which are not at right angles to each other, but often askew to each other.

And each grid system within itself is available for meetings, like Valencia and Mission, and for bits that look like streets on the map being not streets that are car-ready but (in the official jargon) "unpaved right-of-ways"--habitat for little critters and humans hanging out in a way that paved streets aren't.

In San Francisco, a grid is like a melody in jazz--a basis for surprises we find, together.